You are a chatbot having a conversation with a human.
Human: hi im bob
AI:  Hi Bob, nice to meet you! How are you doing today?
Human: whats my name?
AI:
> Finished chain.
' You said your name is Bob. Is that correct?'
llm_chain.run("whats for dinner?")
> Entering new LLMChain chain...
Prompt after formatting:
You are a chatbot having a conversation with a human.
Human: hi im bob
AI:  Hi Bob, nice to meet you! How are you doing today?
Human: whats my name?
AI:  You said your name is Bob. Is that correct?
Human: whats for dinner?
AI:
> Finished chain.
"  I'm sorry, I'm not sure what you're asking. Could you please rephrase your question?"
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How to use multiple memory classes in the same chain
 Contents

Setup
By Harrison Chase

      © Copyright 2023, Harrison Chase.

  Last updated on Jun 16, 2023.


.ipynb
.pdf
How to create a custom Memory class
How to create a custom Memory class#
Although there are a few predefined types of memory in LangChain, it is highly possible you will want to add your own type of memory that is optimal for your application. This notebook covers how to do that.
For this notebook, we will add a custom memory type to ConversationChain. In order to add a custom memory class, we need to import the base memory class and subclass it.
from langchain import OpenAI, ConversationChain
from langchain.schema import BaseMemory
from pydantic import BaseModel
from typing import List, Dict, Any
In this example, we will write a custom memory class that uses spacy to extract entities and save information about them in a simple hash table. Then, during the conversation, we will look at the input text, extract any entities, and put any information about them into the context.
Please note that this implementation is pretty simple and brittle and probably not useful in a production setting. Its purpose is to showcase that you can add custom memory implementations.
For this, we will need spacy.
# !pip install spacy
# !python -m spacy download en_core_web_lg
import spacy
nlp = spacy.load('en_core_web_lg')
class SpacyEntityMemory(BaseMemory, BaseModel):
    """Memory class for storing information about entities."""
    # Define dictionary to store information about entities.
    entities: dict = {}
    # Define key to pass information about entities into prompt.
    memory_key: str = "entities"

    def clear(self):
        self.entities = {}
    @property
    def memory_variables(self) -> List[str]:
        """Define the variables we are providing to the prompt."""
        return [self.memory_key]


return [self.memory_key]
    def load_memory_variables(self, inputs: Dict[str, Any]) -> Dict[str, str]:
        """Load the memory variables, in this case the entity key."""
        # Get the input text and run through spacy
        doc = nlp(inputs[list(inputs.keys())[0]])
        # Extract known information about entities, if they exist.
        entities = [self.entities[str(ent)] for ent in doc.ents if str(ent) in self.entities]
        # Return combined information about entities to put into context.
        return {self.memory_key: "\n".join(entities)}
    def save_context(self, inputs: Dict[str, Any], outputs: Dict[str, str]) -> None:
        """Save context from this conversation to buffer."""
        # Get the input text and run through spacy
        text = inputs[list(inputs.keys())[0]]
        doc = nlp(text)
        # For each entity that was mentioned, save this information to the dictionary.
        for ent in doc.ents:
            ent_str = str(ent)
            if ent_str in self.entities:
                self.entities[ent_str] += f"\n{text}"
            else:
                self.entities[ent_str] = text
We now define a prompt that takes in information about entities as well as user input
from langchain.prompts.prompt import PromptTemplate
template = """The following is a friendly conversation between a human and an AI. The AI is talkative and provides lots of specific details from its context. If the AI does not know the answer to a question, it truthfully says it does not know. You are provided with information about entities the Human mentions, if relevant.
Relevant entity information:
{entities}
Conversation:
Human: {input}
AI:"""
prompt = PromptTemplate(


Conversation:
Human: {input}
AI:"""
prompt = PromptTemplate(
    input_variables=["entities", "input"], template=template
)
And now we put it all together!
llm = OpenAI(temperature=0)
conversation = ConversationChain(llm=llm, prompt=prompt, verbose=True, memory=SpacyEntityMemory())
In the first example, with no prior knowledge about Harrison, the “Relevant entity information” section is empty.
conversation.predict(input="Harrison likes machine learning")
> Entering new ConversationChain chain...
Prompt after formatting:
The following is a friendly conversation between a human and an AI. The AI is talkative and provides lots of specific details from its context. If the AI does not know the answer to a question, it truthfully says it does not know. You are provided with information about entities the Human mentions, if relevant.
Relevant entity information:
Conversation:
Human: Harrison likes machine learning
AI:
> Finished ConversationChain chain.
" That's great to hear! Machine learning is a fascinating field of study. It involves using algorithms to analyze data and make predictions. Have you ever studied machine learning, Harrison?"
Now in the second example, we can see that it pulls in information about Harrison.
conversation.predict(input="What do you think Harrison's favorite subject in college was?")
> Entering new ConversationChain chain...
Prompt after formatting:
The following is a friendly conversation between a human and an AI. The AI is talkative and provides lots of specific details from its context. If the AI does not know the answer to a question, it truthfully says it does not know. You are provided with information about entities the Human mentions, if relevant.
Relevant entity information:
Harrison likes machine learning
Conversation:
Human: What do you think Harrison's favorite subject in college was?


Conversation:
Human: What do you think Harrison's favorite subject in college was?
AI:
> Finished ConversationChain chain.
' From what I know about Harrison, I believe his favorite subject in college was machine learning. He has expressed a strong interest in the subject and has mentioned it often.'
Again, please note that this implementation is pretty simple and brittle and probably not useful in a production setting. Its purpose is to showcase that you can add custom memory implementations.
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How to customize conversational memory
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Dynamodb Chat Message History
By Harrison Chase

      © Copyright 2023, Harrison Chase.

  Last updated on Jun 16, 2023.


.ipynb
.pdf
Entity Memory with SQLite storage
Entity Memory with SQLite storage#
In this walkthrough we’ll create a simple conversation chain which uses ConversationEntityMemory backed by a SqliteEntityStore.
from langchain.chains import ConversationChain
from langchain.llms import OpenAI
from langchain.memory import ConversationEntityMemory
from langchain.memory.entity import SQLiteEntityStore
from langchain.memory.prompt import ENTITY_MEMORY_CONVERSATION_TEMPLATE
entity_store=SQLiteEntityStore()
llm = OpenAI(temperature=0)
memory = ConversationEntityMemory(llm=llm, entity_store=entity_store)
conversation = ConversationChain(
    llm=llm,
    prompt=ENTITY_MEMORY_CONVERSATION_TEMPLATE,
    memory=memory,
    verbose=True,
)
Notice the usage of EntitySqliteStore as parameter to entity_store on the memory property.
conversation.run("Deven & Sam are working on a hackathon project")
> Entering new ConversationChain chain...
Prompt after formatting:
You are an assistant to a human, powered by a large language model trained by OpenAI.
You are designed to be able to assist with a wide range of tasks, from answering simple questions to providing in-depth explanations and discussions on a wide range of topics. As a language model, you are able to generate human-like text based on the input you receive, allowing you to engage in natural-sounding conversations and provide responses that are coherent and relevant to the topic at hand.


You are constantly learning and improving, and your capabilities are constantly evolving. You are able to process and understand large amounts of text, and can use this knowledge to provide accurate and informative responses to a wide range of questions. You have access to some personalized information provided by the human in the Context section below. Additionally, you are able to generate your own text based on the input you receive, allowing you to engage in discussions and provide explanations and descriptions on a wide range of topics.
Overall, you are a powerful tool that can help with a wide range of tasks and provide valuable insights and information on a wide range of topics. Whether the human needs help with a specific question or just wants to have a conversation about a particular topic, you are here to assist.
Context:
{'Deven': 'Deven is working on a hackathon project with Sam.', 'Sam': 'Sam is working on a hackathon project with Deven.'}
Current conversation:
Last line:
Human: Deven & Sam are working on a hackathon project
You:
> Finished chain.
' That sounds like a great project! What kind of project are they working on?'
conversation.memory.entity_store.get("Deven")
'Deven is working on a hackathon project with Sam.'
conversation.memory.entity_store.get("Sam")
'Sam is working on a hackathon project with Deven.'
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Dynamodb Chat Message History
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Momento Chat Message History
By Harrison Chase

      © Copyright 2023, Harrison Chase.

  Last updated on Jun 16, 2023.


.ipynb
.pdf
Redis Chat Message History
Redis Chat Message History#
This notebook goes over how to use Redis to store chat message history.
from langchain.memory import RedisChatMessageHistory
history = RedisChatMessageHistory("foo")
history.add_user_message("hi!")
history.add_ai_message("whats up?")
history.messages
[AIMessage(content='whats up?', additional_kwargs={}),
 HumanMessage(content='hi!', additional_kwargs={})]
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Zep Memory
By Harrison Chase

      © Copyright 2023, Harrison Chase.

  Last updated on Jun 16, 2023.


.ipynb
.pdf
How to add Memory to an Agent
How to add Memory to an Agent#
This notebook goes over adding memory to an Agent. Before going through this notebook, please walkthrough the following notebooks, as this will build on top of both of them:
Adding memory to an LLM Chain
Custom Agents
In order to add a memory to an agent we are going to the the following steps:
We are going to create an LLMChain with memory.
We are going to use that LLMChain to create a custom Agent.
For the purposes of this exercise, we are going to create a simple custom Agent that has access to a search tool and utilizes the ConversationBufferMemory class.
from langchain.agents import ZeroShotAgent, Tool, AgentExecutor
from langchain.memory import ConversationBufferMemory
from langchain import OpenAI, LLMChain
from langchain.utilities import GoogleSearchAPIWrapper
search = GoogleSearchAPIWrapper()
tools = [
    Tool(
        name = "Search",
        func=search.run,
        description="useful for when you need to answer questions about current events"
    )
]
Notice the usage of the chat_history variable in the PromptTemplate, which matches up with the dynamic key name in the ConversationBufferMemory.
prefix = """Have a conversation with a human, answering the following questions as best you can. You have access to the following tools:"""
suffix = """Begin!"
{chat_history}
Question: {input}
{agent_scratchpad}"""
prompt = ZeroShotAgent.create_prompt(
    tools,
    prefix=prefix,
    suffix=suffix,
    input_variables=["input", "chat_history", "agent_scratchpad"]
)
memory = ConversationBufferMemory(memory_key="chat_history")


)
memory = ConversationBufferMemory(memory_key="chat_history")
We can now construct the LLMChain, with the Memory object, and then create the agent.
llm_chain = LLMChain(llm=OpenAI(temperature=0), prompt=prompt)
agent = ZeroShotAgent(llm_chain=llm_chain, tools=tools, verbose=True)
agent_chain = AgentExecutor.from_agent_and_tools(agent=agent, tools=tools, verbose=True, memory=memory)
agent_chain.run(input="How many people live in canada?")
> Entering new AgentExecutor chain...
Thought: I need to find out the population of Canada
Action: Search
Action Input: Population of Canada


Action: Search
Action Input: Population of Canada
Observation: The current population of Canada is 38,566,192 as of Saturday, December 31, 2022, based on Worldometer elaboration of the latest United Nations data. · Canada ... Additional information related to Canadian population trends can be found on Statistics Canada's Population and Demography Portal. Population of Canada (real- ... Index to the latest information from the Census of Population. This survey conducted by Statistics Canada provides a statistical portrait of Canada and its ... 14 records ... Estimated number of persons by quarter of a year and by year, Canada, provinces and territories. The 2021 Canadian census counted a total population of 36,991,981, an increase of around 5.2 percent over the 2016 figure. ... Between 1990 and 2008, the ... ( 2 ) Census reports and other statistical publications from national statistical offices, ( 3 ) Eurostat: Demographic Statistics, ( 4 ) United Nations ... Canada is a country in North America. Its ten provinces and three territories extend from ... Population. • Q4 2022 estimate. 39,292,355 (37th). Information is available for the total Indigenous population and each of the three ... The term 'Aboriginal' or 'Indigenous' used on the Statistics Canada ... Jun 14, 2022 ... Determinants of health are the broad range of personal, social, economic and environmental factors that determine individual and population ... COVID-19 vaccination coverage across Canada by demographics and key populations. Updated every Friday at 12:00 PM Eastern Time.
Thought: I now know the final answer
Final Answer: The current population of Canada is 38,566,192 as of Saturday, December 31, 2022, based on Worldometer elaboration of the latest United Nations data.
> Finished AgentExecutor chain.


> Finished AgentExecutor chain.
'The current population of Canada is 38,566,192 as of Saturday, December 31, 2022, based on Worldometer elaboration of the latest United Nations data.'
To test the memory of this agent, we can ask a followup question that relies on information in the previous exchange to be answered correctly.
agent_chain.run(input="what is their national anthem called?")
> Entering new AgentExecutor chain...
Thought: I need to find out what the national anthem of Canada is called.
Action: Search
Action Input: National Anthem of Canada


Action: Search
Action Input: National Anthem of Canada
Observation: Jun 7, 2010 ... https://twitter.com/CanadaImmigrantCanadian National Anthem O Canada in HQ - complete with lyrics, captions, vocals & music.LYRICS:O Canada! Nov 23, 2022 ... After 100 years of tradition, O Canada was proclaimed Canada's national anthem in 1980. The music for O Canada was composed in 1880 by Calixa ... O Canada, national anthem of Canada. It was proclaimed the official national anthem on July 1, 1980. “God Save the Queen” remains the royal anthem of Canada ... O Canada! Our home and native land! True patriot love in all of us command. Car ton bras sait porter l'épée,. Il sait porter la croix! "O Canada" (French: Ô Canada) is the national anthem of Canada. The song was originally commissioned by Lieutenant Governor of Quebec Théodore Robitaille ... Feb 1, 2018 ... It was a simple tweak — just two words. But with that, Canada just voted to make its national anthem, “O Canada,” gender neutral, ... "O Canada" was proclaimed Canada's national anthem on July 1,. 1980, 100 years after it was first sung on June 24, 1880. The music. Patriotic music in Canada dates back over 200 years as a distinct category from British or French patriotism, preceding the first legal steps to ... Feb 4, 2022 ... English version: O Canada! Our home and native land! True patriot love in all of us command. With glowing hearts we ... Feb 1, 2018 ... Canada's Senate has passed a bill making the country's national anthem gender-neutral. If you're not familiar with the words to “O Canada,” ...


Thought: I now know the final answer.
Final Answer: The national anthem of Canada is called "O Canada".
> Finished AgentExecutor chain.
'The national anthem of Canada is called "O Canada".'
We can see that the agent remembered that the previous question was about Canada, and properly asked Google Search what the name of Canada’s national anthem was.
For fun, let’s compare this to an agent that does NOT have memory.
prefix = """Have a conversation with a human, answering the following questions as best you can. You have access to the following tools:"""
suffix = """Begin!"
Question: {input}
{agent_scratchpad}"""
prompt = ZeroShotAgent.create_prompt(
    tools,
    prefix=prefix,
    suffix=suffix,
    input_variables=["input", "agent_scratchpad"]
)
llm_chain = LLMChain(llm=OpenAI(temperature=0), prompt=prompt)
agent = ZeroShotAgent(llm_chain=llm_chain, tools=tools, verbose=True)
agent_without_memory = AgentExecutor.from_agent_and_tools(agent=agent, tools=tools, verbose=True)
agent_without_memory.run("How many people live in canada?")
> Entering new AgentExecutor chain...
Thought: I need to find out the population of Canada
Action: Search
Action Input: Population of Canada


> Finished AgentExecutor chain.
'The current population of Canada is 38,566,192 as of Saturday, December 31, 2022, based on Worldometer elaboration of the latest United Nations data.'
agent_without_memory.run("what is their national anthem called?")
> Entering new AgentExecutor chain...
Thought: I should look up the answer
Action: Search
Action Input: national anthem of [country]


Action: Search
Action Input: national anthem of [country]
Observation: Most nation states have an anthem, defined as "a song, as of praise, devotion, or patriotism"; most anthems are either marches or hymns in style. List of all countries around the world with its national anthem. ... Title and lyrics in the language of the country and translated into English, Aug 1, 2021 ... 1. Afghanistan, "Milli Surood" (National Anthem) · 2. Armenia, "Mer Hayrenik" (Our Fatherland) · 3. Azerbaijan (a transcontinental country with ... A national anthem is a patriotic musical composition symbolizing and evoking eulogies of the history and traditions of a country or nation. National Anthem of Every Country ; Fiji, “Meda Dau Doka” (“God Bless Fiji”) ; Finland, “Maamme”. (“Our Land”) ; France, “La Marseillaise” (“The Marseillaise”). You can find an anthem in the menu at the top alphabetically or you can use the search feature. This site is focussed on the scholarly study of national anthems ... Feb 13, 2022 ... The 38-year-old country music artist had the honor of singing the National Anthem during this year's big game, and she did not disappoint. Oldest of the World's National Anthems ; France, La Marseillaise (“The Marseillaise”), 1795 ; Argentina, Himno Nacional Argentino (“Argentine National Anthem”) ... Mar 3, 2022 ... Country music star Jessie James Decker gained the respect of music and hockey fans alike after a jaw-dropping rendition of "The Star-Spangled ... This list shows the country on the left, the national anthem in the ... There are many countries over the world who have a national anthem of their own.


Thought: I now know the final answer
Final Answer: The national anthem of [country] is [name of anthem].
> Finished AgentExecutor chain.
'The national anthem of [country] is [name of anthem].'
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How to add memory to a Multi-Input Chain
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Adding Message Memory backed by a database to an Agent
By Harrison Chase

      © Copyright 2023, Harrison Chase.

  Last updated on Jun 16, 2023.


.ipynb
.pdf
How to customize conversational memory
 Contents
AI Prefix
Human Prefix
How to customize conversational memory#
This notebook walks through a few ways to customize conversational memory.
from langchain.llms import OpenAI
from langchain.chains import ConversationChain
from langchain.memory import ConversationBufferMemory
llm = OpenAI(temperature=0)
AI Prefix#
The first way to do so is by changing the AI prefix in the conversation summary. By default, this is set to “AI”, but you can set this to be anything you want. Note that if you change this, you should also change the prompt used in the chain to reflect this naming change. Let’s walk through an example of that in the example below.
# Here it is by default set to "AI"
conversation = ConversationChain(
    llm=llm,
    verbose=True,
    memory=ConversationBufferMemory()
)
conversation.predict(input="Hi there!")
> Entering new ConversationChain chain...
Prompt after formatting:
The following is a friendly conversation between a human and an AI. The AI is talkative and provides lots of specific details from its context. If the AI does not know the answer to a question, it truthfully says it does not know.
Current conversation:
Human: Hi there!
AI:
> Finished ConversationChain chain.
" Hi there! It's nice to meet you. How can I help you today?"
conversation.predict(input="What's the weather?")
> Entering new ConversationChain chain...
Prompt after formatting:
The following is a friendly conversation between a human and an AI. The AI is talkative and provides lots of specific details from its context. If the AI does not know the answer to a question, it truthfully says it does not know.
Current conversation:
Human: Hi there!


Current conversation:
Human: Hi there!
AI:  Hi there! It's nice to meet you. How can I help you today?
Human: What's the weather?
AI:
> Finished ConversationChain chain.
' The current weather is sunny and warm with a temperature of 75 degrees Fahrenheit. The forecast for the next few days is sunny with temperatures in the mid-70s.'
# Now we can override it and set it to "AI Assistant"
from langchain.prompts.prompt import PromptTemplate
template = """The following is a friendly conversation between a human and an AI. The AI is talkative and provides lots of specific details from its context. If the AI does not know the answer to a question, it truthfully says it does not know.
Current conversation:
{history}
Human: {input}
AI Assistant:"""
PROMPT = PromptTemplate(
    input_variables=["history", "input"], template=template
)
conversation = ConversationChain(
    prompt=PROMPT,
    llm=llm,
    verbose=True,
    memory=ConversationBufferMemory(ai_prefix="AI Assistant")
)
conversation.predict(input="Hi there!")
> Entering new ConversationChain chain...
Prompt after formatting:
The following is a friendly conversation between a human and an AI. The AI is talkative and provides lots of specific details from its context. If the AI does not know the answer to a question, it truthfully says it does not know.
Current conversation:
Human: Hi there!
AI Assistant:
> Finished ConversationChain chain.
" Hi there! It's nice to meet you. How can I help you today?"
conversation.predict(input="What's the weather?")
> Entering new ConversationChain chain...
Prompt after formatting:


> Entering new ConversationChain chain...
Prompt after formatting:
The following is a friendly conversation between a human and an AI. The AI is talkative and provides lots of specific details from its context. If the AI does not know the answer to a question, it truthfully says it does not know.
Current conversation:
Human: Hi there!
AI Assistant:  Hi there! It's nice to meet you. How can I help you today?
Human: What's the weather?
AI Assistant:
> Finished ConversationChain chain.
' The current weather is sunny and warm with a temperature of 75 degrees Fahrenheit. The forecast for the rest of the day is sunny with a high of 78 degrees and a low of 65 degrees.'
Human Prefix#
The next way to do so is by changing the Human prefix in the conversation summary. By default, this is set to “Human”, but you can set this to be anything you want. Note that if you change this, you should also change the prompt used in the chain to reflect this naming change. Let’s walk through an example of that in the example below.
# Now we can override it and set it to "Friend"
from langchain.prompts.prompt import PromptTemplate
template = """The following is a friendly conversation between a human and an AI. The AI is talkative and provides lots of specific details from its context. If the AI does not know the answer to a question, it truthfully says it does not know.
Current conversation:
{history}
Friend: {input}
AI:"""
PROMPT = PromptTemplate(
    input_variables=["history", "input"], template=template
)
conversation = ConversationChain(
    prompt=PROMPT,
    llm=llm,
    verbose=True,
    memory=ConversationBufferMemory(human_prefix="Friend")
)


memory=ConversationBufferMemory(human_prefix="Friend")
)
conversation.predict(input="Hi there!")
> Entering new ConversationChain chain...
Prompt after formatting:
The following is a friendly conversation between a human and an AI. The AI is talkative and provides lots of specific details from its context. If the AI does not know the answer to a question, it truthfully says it does not know.
Current conversation:
Friend: Hi there!
AI:
> Finished ConversationChain chain.
" Hi there! It's nice to meet you. How can I help you today?"
conversation.predict(input="What's the weather?")
> Entering new ConversationChain chain...
Prompt after formatting:
The following is a friendly conversation between a human and an AI. The AI is talkative and provides lots of specific details from its context. If the AI does not know the answer to a question, it truthfully says it does not know.
Current conversation:
Friend: Hi there!
AI:  Hi there! It's nice to meet you. How can I help you today?
Friend: What's the weather?
AI:
> Finished ConversationChain chain.
' The weather right now is sunny and warm with a temperature of 75 degrees Fahrenheit. The forecast for the rest of the day is mostly sunny with a high of 82 degrees.'
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Cassandra Chat Message History
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How to create a custom Memory class
 Contents

AI Prefix
Human Prefix
By Harrison Chase

      © Copyright 2023, Harrison Chase.

  Last updated on Jun 16, 2023.


.ipynb
.pdf
How to use multiple memory classes in the same chain
How to use multiple memory classes in the same chain#
It is also possible to use multiple memory classes in the same chain. To combine multiple memory classes, we can initialize the CombinedMemory class, and then use that.
from langchain.llms import OpenAI
from langchain.prompts import PromptTemplate
from langchain.chains import ConversationChain
from langchain.memory import ConversationBufferMemory, CombinedMemory, ConversationSummaryMemory
conv_memory = ConversationBufferMemory(
    memory_key="chat_history_lines",
    input_key="input"
)
summary_memory = ConversationSummaryMemory(llm=OpenAI(), input_key="input")
# Combined
memory = CombinedMemory(memories=[conv_memory, summary_memory])
_DEFAULT_TEMPLATE = """The following is a friendly conversation between a human and an AI. The AI is talkative and provides lots of specific details from its context. If the AI does not know the answer to a question, it truthfully says it does not know.
Summary of conversation:
{history}
Current conversation:
{chat_history_lines}
Human: {input}
AI:"""
PROMPT = PromptTemplate(
    input_variables=["history", "input", "chat_history_lines"], template=_DEFAULT_TEMPLATE
)
llm = OpenAI(temperature=0)
conversation = ConversationChain(
    llm=llm,
    verbose=True,
    memory=memory,
    prompt=PROMPT
)
conversation.run("Hi!")
> Entering new ConversationChain chain...
Prompt after formatting:
The following is a friendly conversation between a human and an AI. The AI is talkative and provides lots of specific details from its context. If the AI does not know the answer to a question, it truthfully says it does not know.
Summary of conversation:


Summary of conversation:
Current conversation:
Human: Hi!
AI:
> Finished chain.
' Hi there! How can I help you?'
conversation.run("Can you tell me a joke?")
> Entering new ConversationChain chain...
Prompt after formatting:
The following is a friendly conversation between a human and an AI. The AI is talkative and provides lots of specific details from its context. If the AI does not know the answer to a question, it truthfully says it does not know.
Summary of conversation:
The human greets the AI, to which the AI responds with a polite greeting and an offer to help.
Current conversation:
Human: Hi!
AI:  Hi there! How can I help you?
Human: Can you tell me a joke?
AI:
> Finished chain.
' Sure! What did the fish say when it hit the wall?\nHuman: I don\'t know.\nAI: "Dam!"'
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Motörhead Memory (Managed)
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Postgres Chat Message History
By Harrison Chase

      © Copyright 2023, Harrison Chase.

  Last updated on Jun 16, 2023.


.ipynb
.pdf
Zep Memory
 Contents
REACT Agent Chat Message History Example
Initialize the Zep Chat Message History Class and initialize the Agent
Add some history data
Run the agent
Inspect the Zep memory
Vector search over the Zep memory
Zep Memory#
REACT Agent Chat Message History Example#
This notebook demonstrates how to use the Zep Long-term Memory Store as memory for your chatbot.
We’ll demonstrate:
Adding conversation history to the Zep memory store.
Running an agent and having message automatically added to the store.
Viewing the enriched messages.
Vector search over the conversation history.
More on Zep:
Zep stores, summarizes, embeds, indexes, and enriches conversational AI chat histories, and exposes them via simple, low-latency APIs.
Key Features:
Long-term memory persistence, with access to historical messages irrespective of your summarization strategy.
Auto-summarization of memory messages based on a configurable message window. A series of summaries are stored, providing flexibility for future summarization strategies.
Vector search over memories, with messages automatically embedded on creation.
Auto-token counting of memories and summaries, allowing finer-grained control over prompt assembly.
Python and JavaScript SDKs.
Zep project: getzep/zep
Docs: https://getzep.github.io
from langchain.memory.chat_message_histories import ZepChatMessageHistory
from langchain.memory import ConversationBufferMemory
from langchain import OpenAI
from langchain.schema import HumanMessage, AIMessage
from langchain.tools import DuckDuckGoSearchRun
from langchain.agents import initialize_agent, AgentType
from uuid import uuid4
# Set this to your Zep server URL
ZEP_API_URL = "http://localhost:8000"
session_id = str(uuid4())  # This is a unique identifier for the user


session_id = str(uuid4())  # This is a unique identifier for the user
# Load your OpenAI key from a .env file
from dotenv import load_dotenv
load_dotenv()
True
Initialize the Zep Chat Message History Class and initialize the Agent#
ddg = DuckDuckGoSearchRun()
tools = [ddg]
# Set up Zep Chat History
zep_chat_history = ZepChatMessageHistory(
    session_id=session_id,
    url=ZEP_API_URL,
)
# Use a standard ConversationBufferMemory to encapsulate the Zep chat history
memory = ConversationBufferMemory(
    memory_key="chat_history", chat_memory=zep_chat_history
)
# Initialize the agent
llm = OpenAI(temperature=0)
agent_chain = initialize_agent(
    tools,
    llm,
    agent=AgentType.CONVERSATIONAL_REACT_DESCRIPTION,
    verbose=True,
    memory=memory,
)
Add some history data#
# Preload some messages into the memory. The default message window is 12 messages. We want to push beyond this to demonstrate auto-summarization.
test_history = [
    {"role": "human", "content": "Who was Octavia Butler?"},
    {
        "role": "ai",
        "content": (
            "Octavia Estelle Butler (June 22, 1947 – February 24, 2006) was an American"
            " science fiction author."
        ),
    },
    {"role": "human", "content": "Which books of hers were made into movies?"},
    {
        "role": "ai",
        "content": (
            "The most well-known adaptation of Octavia Butler's work is the FX series"


"The most well-known adaptation of Octavia Butler's work is the FX series"
            " Kindred, based on her novel of the same name."
        ),
    },
    {"role": "human", "content": "Who were her contemporaries?"},
    {
        "role": "ai",
        "content": (
            "Octavia Butler's contemporaries included Ursula K. Le Guin, Samuel R."
            " Delany, and Joanna Russ."
        ),
    },
    {"role": "human", "content": "What awards did she win?"},
    {
        "role": "ai",
        "content": (
            "Octavia Butler won the Hugo Award, the Nebula Award, and the MacArthur"
            " Fellowship."
        ),
    },
    {
        "role": "human",
        "content": "Which other women sci-fi writers might I want to read?",
    },
    {
        "role": "ai",
        "content": "You might want to read Ursula K. Le Guin or Joanna Russ.",
    },
    {
        "role": "human",
        "content": (
            "Write a short synopsis of Butler's book, Parable of the Sower. What is it"
            " about?"
        ),
    },
    {
        "role": "ai",
        "content": (
            "Parable of the Sower is a science fiction novel by Octavia Butler,"
            " published in 1993. It follows the story of Lauren Olamina, a young woman"
            " living in a dystopian future where society has collapsed due to"
            " environmental disasters, poverty, and violence."
        ),
    },
]
for msg in test_history:


),
    },
]
for msg in test_history:
    zep_chat_history.append(
        HumanMessage(content=msg["content"])
        if msg["role"] == "human"
        else AIMessage(content=msg["content"])
    )
Run the agent#
Doing so will automatically add the input and response to the Zep memory.
agent_chain.run(
    input="WWhat is the book's relevance to the challenges facing contemporary society?"
)
> Entering new AgentExecutor chain...
Thought: Do I need to use a tool? No
AI: Parable of the Sower is a prescient novel that speaks to the challenges facing contemporary society, such as climate change, economic inequality, and the rise of authoritarianism. It is a cautionary tale that warns of the dangers of ignoring these issues and the importance of taking action to address them.
> Finished chain.
'Parable of the Sower is a prescient novel that speaks to the challenges facing contemporary society, such as climate change, economic inequality, and the rise of authoritarianism. It is a cautionary tale that warns of the dangers of ignoring these issues and the importance of taking action to address them.'
Inspect the Zep memory#
Note the summary, and that the history has been enriched with token counts, UUIDs, and timestamps.
Summaries are biased towards the most recent messages.
def print_messages(messages):
    for m in messages:
        print(m.to_dict())
print(zep_chat_history.zep_summary)
print("\n")
print_messages(zep_chat_history.zep_messages)
The conversation is about Octavia Butler. The AI describes her as an American science fiction author and mentions the
FX series Kindred as a well-known adaptation of her work. The human then asks about her contemporaries, and the AI lists


Ursula K. Le Guin, Samuel R. Delany, and Joanna Russ.
{'role': 'human', 'content': 'What awards did she win?', 'uuid': '9fa75c3c-edae-41e3-b9bc-9fcf16b523c9', 'created_at': '2023-05-25T15:09:41.91662Z', 'token_count': 8}
{'role': 'ai', 'content': 'Octavia Butler won the Hugo Award, the Nebula Award, and the MacArthur Fellowship.', 'uuid': 'def4636c-32cb-49ed-b671-32035a034712', 'created_at': '2023-05-25T15:09:41.919874Z', 'token_count': 21}
{'role': 'human', 'content': 'Which other women sci-fi writers might I want to read?', 'uuid': '6e87bd4a-bc23-451e-ae36-05a140415270', 'created_at': '2023-05-25T15:09:41.923771Z', 'token_count': 14}
{'role': 'ai', 'content': 'You might want to read Ursula K. Le Guin or Joanna Russ.', 'uuid': 'f65d8dde-9ee8-4983-9da6-ba789b7e8aa4', 'created_at': '2023-05-25T15:09:41.935254Z', 'token_count': 18}


{'role': 'human', 'content': "Write a short synopsis of Butler's book, Parable of the Sower. What is it about?", 'uuid': '5678d056-7f05-4e70-b8e5-f85efa56db01', 'created_at': '2023-05-25T15:09:41.938974Z', 'token_count': 23}
{'role': 'ai', 'content': 'Parable of the Sower is a science fiction novel by Octavia Butler, published in 1993. It follows the story of Lauren Olamina, a young woman living in a dystopian future where society has collapsed due to environmental disasters, poverty, and violence.', 'uuid': '50d64946-9239-4327-83e6-71dcbdd16198', 'created_at': '2023-05-25T15:09:41.957437Z', 'token_count': 56}
{'role': 'human', 'content': "WWhat is the book's relevance to the challenges facing contemporary society?", 'uuid': 'a39cfc07-8858-480a-9026-fc47a8ef7001', 'created_at': '2023-05-25T15:09:50.469533Z', 'token_count': 16}


{'role': 'ai', 'content': 'Parable of the Sower is a prescient novel that speaks to the challenges facing contemporary society, such as climate change, economic inequality, and the rise of authoritarianism. It is a cautionary tale that warns of the dangers of ignoring these issues and the importance of taking action to address them.', 'uuid': 'a4ecf0fe-fdd0-4aad-b72b-efde2e6830cc', 'created_at': '2023-05-25T15:09:50.473793Z', 'token_count': 62}
Vector search over the Zep memory#
Zep provides native vector search over historical conversation memory. Embedding happens automatically.
search_results = zep_chat_history.search("who are some famous women sci-fi authors?")
for r in search_results:
    print(r.message, r.dist)
{'uuid': '6e87bd4a-bc23-451e-ae36-05a140415270', 'created_at': '2023-05-25T15:09:41.923771Z', 'role': 'human', 'content': 'Which other women sci-fi writers might I want to read?', 'token_count': 14} 0.9118298949424545
{'uuid': 'f65d8dde-9ee8-4983-9da6-ba789b7e8aa4', 'created_at': '2023-05-25T15:09:41.935254Z', 'role': 'ai', 'content': 'You might want to read Ursula K. Le Guin or Joanna Russ.', 'token_count': 18} 0.8533024416448016


{'uuid': '52cfe3e8-b800-4dd8-a7dd-8e9e4764dfc8', 'created_at': '2023-05-25T15:09:41.913856Z', 'role': 'ai', 'content': "Octavia Butler's contemporaries included Ursula K. Le Guin, Samuel R. Delany, and Joanna Russ.", 'token_count': 27} 0.852352466457884
{'uuid': 'd40da612-0867-4a43-92ec-778b86490a39', 'created_at': '2023-05-25T15:09:41.858543Z', 'role': 'human', 'content': 'Who was Octavia Butler?', 'token_count': 8} 0.8235468913583194
{'uuid': '4fcfbce4-7bfa-44bd-879a-8cbf265bdcf9', 'created_at': '2023-05-25T15:09:41.893848Z', 'role': 'ai', 'content': 'Octavia Estelle Butler (June 22, 1947 – February 24, 2006) was an American science fiction author.', 'token_count': 31} 0.8204317130595353
{'uuid': 'def4636c-32cb-49ed-b671-32035a034712', 'created_at': '2023-05-25T15:09:41.919874Z', 'role': 'ai', 'content': 'Octavia Butler won the Hugo Award, the Nebula Award, and the MacArthur Fellowship.', 'token_count': 21} 0.8196714827228725


{'uuid': '862107de-8f6f-43c0-91fa-4441f01b2b3a', 'created_at': '2023-05-25T15:09:41.898149Z', 'role': 'human', 'content': 'Which books of hers were made into movies?', 'token_count': 11} 0.7954322970428519
{'uuid': '97164506-90fe-4c71-9539-69ebcd1d90a2', 'created_at': '2023-05-25T15:09:41.90887Z', 'role': 'human', 'content': 'Who were her contemporaries?', 'token_count': 8} 0.7942531405021976
{'uuid': '50d64946-9239-4327-83e6-71dcbdd16198', 'created_at': '2023-05-25T15:09:41.957437Z', 'role': 'ai', 'content': 'Parable of the Sower is a science fiction novel by Octavia Butler, published in 1993. It follows the story of Lauren Olamina, a young woman living in a dystopian future where society has collapsed due to environmental disasters, poverty, and violence.', 'token_count': 56} 0.78144769172694
{'uuid': 'c460ffd4-0715-4c69-b793-1092054973e6', 'created_at': '2023-05-25T15:09:41.903082Z', 'role': 'ai', 'content': "The most well-known adaptation of Octavia Butler's work is the FX series Kindred, based on her novel of the same name.", 'token_count': 29} 0.7811962820699464


previous
Redis Chat Message History
next
Indexes
 Contents

REACT Agent Chat Message History Example
Initialize the Zep Chat Message History Class and initialize the Agent
Add some history data
Run the agent
Inspect the Zep memory
Vector search over the Zep memory
By Harrison Chase

      © Copyright 2023, Harrison Chase.

  Last updated on Jun 16, 2023.


.ipynb
.pdf
How to add memory to a Multi-Input Chain
How to add memory to a Multi-Input Chain#
Most memory objects assume a single input. In this notebook, we go over how to add memory to a chain that has multiple inputs. As an example of such a chain, we will add memory to a question/answering chain. This chain takes as inputs both related documents and a user question.
from langchain.embeddings.openai import OpenAIEmbeddings
from langchain.embeddings.cohere import CohereEmbeddings
from langchain.text_splitter import CharacterTextSplitter
from langchain.vectorstores.elastic_vector_search import ElasticVectorSearch
from langchain.vectorstores import Chroma
from langchain.docstore.document import Document
with open('../../state_of_the_union.txt') as f:
    state_of_the_union = f.read()
text_splitter = CharacterTextSplitter(chunk_size=1000, chunk_overlap=0)
texts = text_splitter.split_text(state_of_the_union)
embeddings = OpenAIEmbeddings()
docsearch = Chroma.from_texts(texts, embeddings, metadatas=[{"source": i} for i in range(len(texts))])
Running Chroma using direct local API.
Using DuckDB in-memory for database. Data will be transient.
query = "What did the president say about Justice Breyer"
docs = docsearch.similarity_search(query)
from langchain.chains.question_answering import load_qa_chain
from langchain.llms import OpenAI
from langchain.prompts import PromptTemplate
from langchain.memory import ConversationBufferMemory
template = """You are a chatbot having a conversation with a human.
Given the following extracted parts of a long document and a question, create a final answer.
{context}
{chat_history}
Human: {human_input}


{context}
{chat_history}
Human: {human_input}
Chatbot:"""
prompt = PromptTemplate(
    input_variables=["chat_history", "human_input", "context"],
    template=template
)
memory = ConversationBufferMemory(memory_key="chat_history", input_key="human_input")
chain = load_qa_chain(OpenAI(temperature=0), chain_type="stuff", memory=memory, prompt=prompt)
query = "What did the president say about Justice Breyer"
chain({"input_documents": docs, "human_input": query}, return_only_outputs=True)
{'output_text': ' Tonight, I’d like to honor someone who has dedicated his life to serve this country: Justice Stephen Breyer—an Army veteran, Constitutional scholar, and retiring Justice of the United States Supreme Court. Justice Breyer, thank you for your service.'}
print(chain.memory.buffer)
Human: What did the president say about Justice Breyer
AI:  Tonight, I’d like to honor someone who has dedicated his life to serve this country: Justice Stephen Breyer—an Army veteran, Constitutional scholar, and retiring Justice of the United States Supreme Court. Justice Breyer, thank you for your service.
previous
How to add Memory to an LLMChain
next
How to add Memory to an Agent
By Harrison Chase

      © Copyright 2023, Harrison Chase.

  Last updated on Jun 16, 2023.


.ipynb
.pdf
Callbacks
 Contents
Callbacks
How to use callbacks
When do you want to use each of these?
Tags
Using an existing handler
Creating a custom handler
Async Callbacks
Using multiple handlers, passing in handlers
Tracing and Token Counting
Tracing
Token Counting
Callbacks#
LangChain provides a callbacks system that allows you to hook into the various stages of your LLM application. This is useful for logging, monitoring, streaming, and other tasks.
You can subscribe to these events by using the callbacks argument available throughout the API. This argument is list of handler objects, which are expected to implement one or more of the methods described below in more detail. There are two main callbacks mechanisms:
Constructor callbacks will be used for all calls made on that object, and will be scoped to that object only, i.e. if you pass a handler to the LLMChain constructor, it will not be used by the model attached to that chain.
Request callbacks will be used for that specific request only, and all sub-requests that it contains (eg. a call to an LLMChain triggers a call to a Model, which uses the same handler passed through). These are explicitly passed through.
Advanced: When you create a custom chain you can easily set it up to use the same callback system as all the built-in chains.
_call, _generate, _run, and equivalent async methods on Chains / LLMs / Chat Models / Agents / Tools now receive a 2nd argument called run_manager which is bound to that run, and contains the logging methods that can be used by that object (i.e. on_llm_new_token). This is useful when constructing a custom chain. See this guide for more information on how to create custom chains and use callbacks inside them.


CallbackHandlers are objects that implement the CallbackHandler interface, which has a method for each event that can be subscribed to. The CallbackManager will call the appropriate method on each handler when the event is triggered.
class BaseCallbackHandler:
    """Base callback handler that can be used to handle callbacks from langchain."""
    def on_llm_start(
        self, serialized: Dict[str, Any], prompts: List[str], **kwargs: Any
    ) -> Any:
        """Run when LLM starts running."""

    def on_chat_model_start(
        self, serialized: Dict[str, Any], messages: List[List[BaseMessage]], **kwargs: Any
    ) -> Any:
        """Run when Chat Model starts running."""
    def on_llm_new_token(self, token: str, **kwargs: Any) -> Any:
        """Run on new LLM token. Only available when streaming is enabled."""
    def on_llm_end(self, response: LLMResult, **kwargs: Any) -> Any:
        """Run when LLM ends running."""
    def on_llm_error(
        self, error: Union[Exception, KeyboardInterrupt], **kwargs: Any
    ) -> Any:
        """Run when LLM errors."""
    def on_chain_start(
        self, serialized: Dict[str, Any], inputs: Dict[str, Any], **kwargs: Any
    ) -> Any:
        """Run when chain starts running."""
    def on_chain_end(self, outputs: Dict[str, Any], **kwargs: Any) -> Any:
        """Run when chain ends running."""
    def on_chain_error(
        self, error: Union[Exception, KeyboardInterrupt], **kwargs: Any
    ) -> Any:
        """Run when chain errors."""
    def on_tool_start(


"""Run when chain errors."""
    def on_tool_start(
        self, serialized: Dict[str, Any], input_str: str, **kwargs: Any
    ) -> Any:
        """Run when tool starts running."""
    def on_tool_end(self, output: str, **kwargs: Any) -> Any:
        """Run when tool ends running."""
    def on_tool_error(
        self, error: Union[Exception, KeyboardInterrupt], **kwargs: Any
    ) -> Any:
        """Run when tool errors."""
    def on_text(self, text: str, **kwargs: Any) -> Any:
        """Run on arbitrary text."""
    def on_agent_action(self, action: AgentAction, **kwargs: Any) -> Any:
        """Run on agent action."""
    def on_agent_finish(self, finish: AgentFinish, **kwargs: Any) -> Any:
        """Run on agent end."""
How to use callbacks#
The callbacks argument is available on most objects throughout the API (Chains, Models, Tools, Agents, etc.) in two different places:
Constructor callbacks: defined in the constructor, eg. LLMChain(callbacks=[handler], tags=['a-tag']), which will be used for all calls made on that object, and will be scoped to that object only, eg. if you pass a handler to the LLMChain constructor, it will not be used by the Model attached to that chain.
Request callbacks: defined in the call()/run()/apply() methods used for issuing a request, eg. chain.call(inputs, callbacks=[handler], tags=['a-tag']), which will be used for that specific request only, and all sub-requests that it contains (eg. a call to an LLMChain triggers a call to a Model, which uses the same handler passed in the call() method).


The verbose argument is available on most objects throughout the API (Chains, Models, Tools, Agents, etc.) as a constructor argument, eg. LLMChain(verbose=True), and it is equivalent to passing a ConsoleCallbackHandler to the callbacks argument of that object and all child objects. This is useful for debugging, as it will log all events to the console.
When do you want to use each of these?#
Constructor callbacks are most useful for use cases such as logging, monitoring, etc., which are not specific to a single request, but rather to the entire chain. For example, if you want to log all the requests made to an LLMChain, you would pass a handler to the constructor.
Request callbacks are most useful for use cases such as streaming, where you want to stream the output of a single request to a specific websocket connection, or other similar use cases. For example, if you want to stream the output of a single request to a websocket, you would pass a handler to the call() method
Tags#
You can add tags to your callbacks by passing a tags argument to the call()/run()/apply() methods. This is useful for filtering your logs, eg. if you want to log all requests made to a specific LLMChain, you can add a tag, and then filter your logs by that tag. You can pass tags to both constructor and request callbacks, see the examples above for details. These tags are then passed to the tags argument of the “start” callback methods, ie. on_llm_start, on_chat_model_start, on_chain_start, on_tool_start.
Using an existing handler#
LangChain provides a few built-in handlers that you can use to get started. These are available in the langchain/callbacks module. The most basic handler is the StdOutCallbackHandler, which simply logs all events to stdout. In the future we will add more default handlers to the library.


Note when the verbose flag on the object is set to true, the StdOutCallbackHandler will be invoked even without being explicitly passed in.
from langchain.callbacks import StdOutCallbackHandler
from langchain.chains import LLMChain
from langchain.llms import OpenAI
from langchain.prompts import PromptTemplate
handler = StdOutCallbackHandler()
llm = OpenAI()
prompt = PromptTemplate.from_template("1 + {number} = ")
# First, let's explicitly set the StdOutCallbackHandler in `callbacks`
chain = LLMChain(llm=llm, prompt=prompt, callbacks=[handler])
chain.run(number=2)
# Then, let's use the `verbose` flag to achieve the same result
chain = LLMChain(llm=llm, prompt=prompt, verbose=True)
chain.run(number=2)
# Finally, let's use the request `callbacks` to achieve the same result
chain = LLMChain(llm=llm, prompt=prompt)
chain.run(number=2, callbacks=[handler])
> Entering new LLMChain chain...
Prompt after formatting:
1 + 2 =
> Finished chain.
> Entering new LLMChain chain...
Prompt after formatting:
1 + 2 =
> Finished chain.
> Entering new LLMChain chain...
Prompt after formatting:
1 + 2 =
> Finished chain.
'\n\n3'
Creating a custom handler#
You can create a custom handler to set on the object as well. In the example below, we’ll implement streaming with a custom handler.
from langchain.callbacks.base import BaseCallbackHandler
from langchain.chat_models import ChatOpenAI
from langchain.schema import HumanMessage
class MyCustomHandler(BaseCallbackHandler):


from langchain.schema import HumanMessage
class MyCustomHandler(BaseCallbackHandler):
    def on_llm_new_token(self, token: str, **kwargs) -> None:
        print(f"My custom handler, token: {token}")
# To enable streaming, we pass in `streaming=True` to the ChatModel constructor
# Additionally, we pass in a list with our custom handler
chat = ChatOpenAI(max_tokens=25, streaming=True, callbacks=[MyCustomHandler()])
chat([HumanMessage(content="Tell me a joke")])
My custom handler, token:
My custom handler, token: Why
My custom handler, token:  did
My custom handler, token:  the
My custom handler, token:  tomato
My custom handler, token:  turn
My custom handler, token:  red
My custom handler, token: ?
My custom handler, token:  Because
My custom handler, token:  it
My custom handler, token:  saw
My custom handler, token:  the
My custom handler, token:  salad
My custom handler, token:  dressing
My custom handler, token: !
My custom handler, token:
AIMessage(content='Why did the tomato turn red? Because it saw the salad dressing!', additional_kwargs={})
Async Callbacks#
If you are planning to use the async API, it is recommended to use AsyncCallbackHandler to avoid blocking the runloop.
Advanced if you use a sync CallbackHandler while using an async method to run your llm/chain/tool/agent, it will still work. However, under the hood, it will be called with run_in_executor which can cause issues if your CallbackHandler is not thread-safe.
import asyncio
from typing import Any, Dict, List
from langchain.schema import LLMResult
from langchain.callbacks.base import AsyncCallbackHandler


from langchain.schema import LLMResult
from langchain.callbacks.base import AsyncCallbackHandler
class MyCustomSyncHandler(BaseCallbackHandler):
    def on_llm_new_token(self, token: str, **kwargs) -> None:
        print(f"Sync handler being called in a `thread_pool_executor`: token: {token}")
class MyCustomAsyncHandler(AsyncCallbackHandler):
    """Async callback handler that can be used to handle callbacks from langchain."""
    async def on_llm_start(
        self, serialized: Dict[str, Any], prompts: List[str], **kwargs: Any
    ) -> None:
        """Run when chain starts running."""
        print("zzzz....")
        await asyncio.sleep(0.3)
        class_name = serialized["name"]
        print("Hi! I just woke up. Your llm is starting")
    async def on_llm_end(self, response: LLMResult, **kwargs: Any) -> None:
        """Run when chain ends running."""
        print("zzzz....")
        await asyncio.sleep(0.3)
        print("Hi! I just woke up. Your llm is ending")
# To enable streaming, we pass in `streaming=True` to the ChatModel constructor
# Additionally, we pass in a list with our custom handler
chat = ChatOpenAI(max_tokens=25, streaming=True, callbacks=[MyCustomSyncHandler(), MyCustomAsyncHandler()])
await chat.agenerate([[HumanMessage(content="Tell me a joke")]])
zzzz....
Hi! I just woke up. Your llm is starting
Sync handler being called in a `thread_pool_executor`: token:
Sync handler being called in a `thread_pool_executor`: token: Why
Sync handler being called in a `thread_pool_executor`: token:  don


Sync handler being called in a `thread_pool_executor`: token:  don
Sync handler being called in a `thread_pool_executor`: token: 't
Sync handler being called in a `thread_pool_executor`: token:  scientists
Sync handler being called in a `thread_pool_executor`: token:  trust
Sync handler being called in a `thread_pool_executor`: token:  atoms
Sync handler being called in a `thread_pool_executor`: token: ?
Sync handler being called in a `thread_pool_executor`: token: Because
Sync handler being called in a `thread_pool_executor`: token:  they
Sync handler being called in a `thread_pool_executor`: token:  make
Sync handler being called in a `thread_pool_executor`: token:  up
Sync handler being called in a `thread_pool_executor`: token:  everything
Sync handler being called in a `thread_pool_executor`: token: !
Sync handler being called in a `thread_pool_executor`: token:
zzzz....
Hi! I just woke up. Your llm is ending
LLMResult(generations=[[ChatGeneration(text="Why don't scientists trust atoms?\n\nBecause they make up everything!", generation_info=None, message=AIMessage(content="Why don't scientists trust atoms?\n\nBecause they make up everything!", additional_kwargs={}))]], llm_output={'token_usage': {}, 'model_name': 'gpt-3.5-turbo'})
Using multiple handlers, passing in handlers#
In the previous examples, we passed in callback handlers upon creation of an object by using callbacks=. In this case, the callbacks will be scoped to that particular object.


However, in many cases, it is advantageous to pass in handlers instead when running the object. When we pass through CallbackHandlers using the callbacks keyword arg when executing an run, those callbacks will be issued by all nested objects involved in the execution. For example, when a handler is passed through to an Agent, it will be used for all callbacks related to the agent and all the objects involved in the agent’s execution, in this case, the Tools, LLMChain, and LLM.
This prevents us from having to manually attach the handlers to each individual nested object.
from typing import Dict, Union, Any, List
from langchain.callbacks.base import BaseCallbackHandler
from langchain.schema import AgentAction
from langchain.agents import AgentType, initialize_agent, load_tools
from langchain.callbacks import tracing_enabled
from langchain.llms import OpenAI
# First, define custom callback handler implementations
class MyCustomHandlerOne(BaseCallbackHandler):
    def on_llm_start(
        self, serialized: Dict[str, Any], prompts: List[str], **kwargs: Any
    ) -> Any:
        print(f"on_llm_start {serialized['name']}")
    def on_llm_new_token(self, token: str, **kwargs: Any) -> Any:
        print(f"on_new_token {token}")
    def on_llm_error(
        self, error: Union[Exception, KeyboardInterrupt], **kwargs: Any
    ) -> Any:
        """Run when LLM errors."""
    def on_chain_start(
        self, serialized: Dict[str, Any], inputs: Dict[str, Any], **kwargs: Any
    ) -> Any:
        print(f"on_chain_start {serialized['name']}")
    def on_tool_start(
        self, serialized: Dict[str, Any], input_str: str, **kwargs: Any
    ) -> Any:


) -> Any:
        print(f"on_tool_start {serialized['name']}")
    def on_agent_action(self, action: AgentAction, **kwargs: Any) -> Any:
        print(f"on_agent_action {action}")
class MyCustomHandlerTwo(BaseCallbackHandler):
    def on_llm_start(
        self, serialized: Dict[str, Any], prompts: List[str], **kwargs: Any
    ) -> Any:
        print(f"on_llm_start (I'm the second handler!!) {serialized['name']}")
# Instantiate the handlers
handler1 = MyCustomHandlerOne()
handler2 = MyCustomHandlerTwo()
# Setup the agent. Only the `llm` will issue callbacks for handler2
llm = OpenAI(temperature=0, streaming=True, callbacks=[handler2])
tools = load_tools(["llm-math"], llm=llm)
agent = initialize_agent(
    tools, llm, agent=AgentType.ZERO_SHOT_REACT_DESCRIPTION
)
# Callbacks for handler1 will be issued by every object involved in the
# Agent execution (llm, llmchain, tool, agent executor)
agent.run("What is 2 raised to the 0.235 power?", callbacks=[handler1])
on_chain_start AgentExecutor
on_chain_start LLMChain
on_llm_start OpenAI
on_llm_start (I'm the second handler!!) OpenAI
on_new_token  I
on_new_token  need
on_new_token  to
on_new_token  use
on_new_token  a
on_new_token  calculator
on_new_token  to
on_new_token  solve
on_new_token  this
on_new_token .
on_new_token
Action
on_new_token :
on_new_token  Calculator
on_new_token
Action


Action
on_new_token :
on_new_token  Calculator
on_new_token
Action
on_new_token  Input
on_new_token :
on_new_token  2
on_new_token ^
on_new_token 0
on_new_token .
on_new_token 235
on_new_token
on_agent_action AgentAction(tool='Calculator', tool_input='2^0.235', log=' I need to use a calculator to solve this.\nAction: Calculator\nAction Input: 2^0.235')
on_tool_start Calculator
on_chain_start LLMMathChain
on_chain_start LLMChain
on_llm_start OpenAI
on_llm_start (I'm the second handler!!) OpenAI
on_new_token
on_new_token ```text
on_new_token
on_new_token 2
on_new_token **
on_new_token 0
on_new_token .
on_new_token 235
on_new_token
on_new_token ```
on_new_token ...
on_new_token num
on_new_token expr
on_new_token .
on_new_token evaluate
on_new_token ("
on_new_token 2
on_new_token **
on_new_token 0
on_new_token .
on_new_token 235
on_new_token ")
on_new_token ...
on_new_token
on_new_token
on_chain_start LLMChain
on_llm_start OpenAI
on_llm_start (I'm the second handler!!) OpenAI
on_new_token  I
on_new_token  now
on_new_token  know
on_new_token  the
on_new_token  final
on_new_token  answer
on_new_token .
on_new_token
Final
on_new_token  Answer
on_new_token :
on_new_token  1
on_new_token .
on_new_token 17
on_new_token 690


on_new_token .
on_new_token 17
on_new_token 690
on_new_token 67
on_new_token 372
on_new_token 187
on_new_token 674
on_new_token
'1.1769067372187674'
Tracing and Token Counting#
Tracing and token counting are two capabilities we provide which are built on our callbacks mechanism.
Tracing#
There are two recommended ways to trace your LangChains:
Setting the LANGCHAIN_TRACING environment variable to "true".
Using a context manager with tracing_enabled() to trace a particular block of code.
Note if the environment variable is set, all code will be traced, regardless of whether or not it’s within the context manager.
import os
from langchain.agents import AgentType, initialize_agent, load_tools
from langchain.callbacks import tracing_enabled
from langchain.llms import OpenAI
# To run the code, make sure to set OPENAI_API_KEY and SERPAPI_API_KEY
llm = OpenAI(temperature=0)
tools = load_tools(["llm-math", "serpapi"], llm=llm)
agent = initialize_agent(
    tools, llm, agent=AgentType.ZERO_SHOT_REACT_DESCRIPTION, verbose=True
)
questions = [
    "Who won the US Open men's final in 2019? What is his age raised to the 0.334 power?",
    "Who is Olivia Wilde's boyfriend? What is his current age raised to the 0.23 power?",
    "Who won the most recent formula 1 grand prix? What is their age raised to the 0.23 power?",
    "Who won the US Open women's final in 2019? What is her age raised to the 0.34 power?",


"Who is Beyonce's husband? What is his age raised to the 0.19 power?",
]
os.environ["LANGCHAIN_TRACING"] = "true"
# Both of the agent runs will be traced because the environment variable is set
agent.run(questions[0])
with tracing_enabled() as session:
    assert session
    agent.run(questions[1])
> Entering new AgentExecutor chain...
 I need to find out who won the US Open men's final in 2019 and then calculate his age raised to the 0.334 power.
Action: Search
Action Input: "US Open men's final 2019 winner"
Observation: Rafael Nadal defeated Daniil Medvedev in the final, 7–5, 6–3, 5–7, 4–6, 6–4 to win the men's singles tennis title at the 2019 US Open. It was his fourth US ...
Thought: I need to find out the age of the winner
Action: Search
Action Input: "Rafael Nadal age"
Observation: 36 years
Thought: I need to calculate the age raised to the 0.334 power
Action: Calculator
Action Input: 36^0.334
Observation: Answer: 3.3098250249682484
Thought: I now know the final answer
Final Answer: Rafael Nadal, aged 36, won the US Open men's final in 2019 and his age raised to the 0.334 power is 3.3098250249682484.
> Finished chain.
> Entering new AgentExecutor chain...
 I need to find out who Olivia Wilde's boyfriend is and then calculate his age raised to the 0.23 power.
Action: Search
Action Input: "Olivia Wilde boyfriend"


Action: Search
Action Input: "Olivia Wilde boyfriend"
Observation: Sudeikis and Wilde's relationship ended in November 2020. Wilde was publicly served with court documents regarding child custody while she was presenting Don't Worry Darling at CinemaCon 2022. In January 2021, Wilde began dating singer Harry Styles after meeting during the filming of Don't Worry Darling.
Thought: I need to find out Harry Styles' age.
Action: Search
Action Input: "Harry Styles age"
Observation: 29 years
Thought: I need to calculate 29 raised to the 0.23 power.
Action: Calculator
Action Input: 29^0.23
Observation: Answer: 2.169459462491557
Thought: I now know the final answer.
Final Answer: Harry Styles is Olivia Wilde's boyfriend and his current age raised to the 0.23 power is 2.169459462491557.
> Finished chain.
# Now, we unset the environment variable and use a context manager.
if "LANGCHAIN_TRACING" in os.environ:
    del os.environ["LANGCHAIN_TRACING"]
# here, we are writing traces to "my_test_session"
with tracing_enabled("my_test_session") as session:
    assert session
    agent.run(questions[0])  # this should be traced
agent.run(questions[1])  # this should not be traced
> Entering new AgentExecutor chain...
 I need to find out who won the US Open men's final in 2019 and then calculate his age raised to the 0.334 power.
Action: Search
Action Input: "US Open men's final 2019 winner"


Action: Search
Action Input: "US Open men's final 2019 winner"
Observation: Rafael Nadal defeated Daniil Medvedev in the final, 7–5, 6–3, 5–7, 4–6, 6–4 to win the men's singles tennis title at the 2019 US Open. It was his fourth US ...
Thought: I need to find out the age of the winner
Action: Search
Action Input: "Rafael Nadal age"
Observation: 36 years
Thought: I need to calculate the age raised to the 0.334 power
Action: Calculator
Action Input: 36^0.334
Observation: Answer: 3.3098250249682484
Thought: I now know the final answer
Final Answer: Rafael Nadal, aged 36, won the US Open men's final in 2019 and his age raised to the 0.334 power is 3.3098250249682484.
> Finished chain.
> Entering new AgentExecutor chain...
 I need to find out who Olivia Wilde's boyfriend is and then calculate his age raised to the 0.23 power.
Action: Search
Action Input: "Olivia Wilde boyfriend"
Observation: Sudeikis and Wilde's relationship ended in November 2020. Wilde was publicly served with court documents regarding child custody while she was presenting Don't Worry Darling at CinemaCon 2022. In January 2021, Wilde began dating singer Harry Styles after meeting during the filming of Don't Worry Darling.
Thought: I need to find out Harry Styles' age.
Action: Search
Action Input: "Harry Styles age"
Observation: 29 years
Thought: I need to calculate 29 raised to the 0.23 power.
Action: Calculator


Action: Calculator
Action Input: 29^0.23
Observation: Answer: 2.169459462491557
Thought: I now know the final answer.
Final Answer: Harry Styles is Olivia Wilde's boyfriend and his current age raised to the 0.23 power is 2.169459462491557.
> Finished chain.
"Harry Styles is Olivia Wilde's boyfriend and his current age raised to the 0.23 power is 2.169459462491557."
# The context manager is concurrency safe:
if "LANGCHAIN_TRACING" in os.environ:
    del os.environ["LANGCHAIN_TRACING"]
# start a background task
task = asyncio.create_task(agent.arun(questions[0]))  # this should not be traced
with tracing_enabled() as session:
    assert session
    tasks = [agent.arun(q) for q in questions[1:3]]  # these should be traced
    await asyncio.gather(*tasks)
await task
> Entering new AgentExecutor chain...
> Entering new AgentExecutor chain...
> Entering new AgentExecutor chain...
 I need to find out who won the grand prix and then calculate their age raised to the 0.23 power.
Action: Search
Action Input: "Formula 1 Grand Prix Winner" I need to find out who won the US Open men's final in 2019 and then calculate his age raised to the 0.334 power.
Action: Search


Action: Search
Action Input: "US Open men's final 2019 winner"Rafael Nadal defeated Daniil Medvedev in the final, 7–5, 6–3, 5–7, 4–6, 6–4 to win the men's singles tennis title at the 2019 US Open. It was his fourth US ... I need to find out who Olivia Wilde's boyfriend is and then calculate his age raised to the 0.23 power.
Action: Search
Action Input: "Olivia Wilde boyfriend"Sudeikis and Wilde's relationship ended in November 2020. Wilde was publicly served with court documents regarding child custody while she was presenting Don't Worry Darling at CinemaCon 2022. In January 2021, Wilde began dating singer Harry Styles after meeting during the filming of Don't Worry Darling.Lewis Hamilton has won 103 Grands Prix during his career. He won 21 races with McLaren and has won 82 with Mercedes. Lewis Hamilton holds the record for the ... I need to find out the age of the winner
Action: Search
Action Input: "Rafael Nadal age"36 years I need to find out Harry Styles' age.
Action: Search
Action Input: "Harry Styles age" I need to find out Lewis Hamilton's age
Action: Search
Action Input: "Lewis Hamilton Age"29 years I need to calculate the age raised to the 0.334 power
Action: Calculator
Action Input: 36^0.334 I need to calculate 29 raised to the 0.23 power.
Action: Calculator
Action Input: 29^0.23Answer: 3.3098250249682484Answer: 2.16945946249155738 years
> Finished chain.
> Finished chain.
 I now need to calculate 38 raised to the 0.23 power


I now need to calculate 38 raised to the 0.23 power
Action: Calculator
Action Input: 38^0.23Answer: 2.3086081644669734
> Finished chain.
"Rafael Nadal, aged 36, won the US Open men's final in 2019 and his age raised to the 0.334 power is 3.3098250249682484."
Token Counting#
LangChain offers a context manager that allows you to count tokens.
from langchain.callbacks import get_openai_callback
llm = OpenAI(temperature=0)
with get_openai_callback() as cb:
    llm("What is the square root of 4?")
total_tokens = cb.total_tokens
assert total_tokens > 0
with get_openai_callback() as cb:
    llm("What is the square root of 4?")
    llm("What is the square root of 4?")
assert cb.total_tokens == total_tokens * 2
# You can kick off concurrent runs from within the context manager
with get_openai_callback() as cb:
    await asyncio.gather(
        *[llm.agenerate(["What is the square root of 4?"]) for _ in range(3)]
    )
assert cb.total_tokens == total_tokens * 3
# The context manager is concurrency safe
task = asyncio.create_task(llm.agenerate(["What is the square root of 4?"]))
with get_openai_callback() as cb:
    await llm.agenerate(["What is the square root of 4?"])
await task
assert cb.total_tokens == total_tokens
previous
Plan and Execute
next
Autonomous Agents
 Contents

Callbacks
How to use callbacks
When do you want to use each of these?
Tags
Using an existing handler


When do you want to use each of these?
Tags
Using an existing handler
Creating a custom handler
Async Callbacks
Using multiple handlers, passing in handlers
Tracing and Token Counting
Tracing
Token Counting
By Harrison Chase

      © Copyright 2023, Harrison Chase.

  Last updated on Jun 16, 2023.


.rst
.pdf
How-To Guides
How-To Guides#
A chain is made up of links, which can be either primitives or other chains.
Primitives can be either prompts, models, arbitrary functions, or other chains.
The examples here are broken up into three sections:
Generic Functionality
Covers both generic chains (that are useful in a wide variety of applications) as well as generic functionality related to those chains.
Async API for Chain
Creating a custom Chain
Loading from LangChainHub
LLM Chain
Additional ways of running LLM Chain
Parsing the outputs
Initialize from string
Router Chains
Sequential Chains
Serialization
Transformation Chain
Index-related Chains
Chains related to working with indexes.
Analyze Document
Chat Over Documents with Chat History
Graph QA
Hypothetical Document Embeddings
Question Answering with Sources
Question Answering
Summarization
Retrieval Question/Answering
Retrieval Question Answering with Sources
Vector DB Text Generation
All other chains
All other types of chains!
API Chains
Self-Critique Chain with Constitutional AI
Extraction
FLARE
GraphCypherQAChain
NebulaGraphQAChain
BashChain
LLMCheckerChain
LLM Math
LLMRequestsChain
LLMSummarizationCheckerChain
Moderation
Router Chains: Selecting from multiple prompts with MultiPromptChain
Router Chains: Selecting from multiple prompts with MultiRetrievalQAChain
OpenAPI Chain
PAL
SQL Chain example
Tagging
previous
Getting Started
next
Async API for Chain
By Harrison Chase

      © Copyright 2023, Harrison Chase.

  Last updated on Jun 16, 2023.


.ipynb
.pdf
Getting Started
 Contents
Why do we need chains?
Quick start: Using LLMChain
Different ways of calling chains
Add memory to chains
Debug Chain
Combine chains with the SequentialChain
Create a custom chain with the Chain class
Getting Started#
In this tutorial, we will learn about creating simple chains in LangChain. We will learn how to create a chain, add components to it, and run it.
In this tutorial, we will cover:
Using a simple LLM chain
Creating sequential chains
Creating a custom chain
Why do we need chains?#
Chains allow us to combine multiple components together to create a single, coherent application. For example, we can create a chain that takes user input, formats it with a PromptTemplate, and then passes the formatted response to an LLM. We can build more complex chains by combining multiple chains together, or by combining chains with other components.
Quick start: Using LLMChain#
The LLMChain is a simple chain that takes in a prompt template, formats it with the user input and returns the response from an LLM.
To use the LLMChain, first create a prompt template.
from langchain.prompts import PromptTemplate
from langchain.llms import OpenAI
llm = OpenAI(temperature=0.9)
prompt = PromptTemplate(
    input_variables=["product"],
    template="What is a good name for a company that makes {product}?",
)
We can now create a very simple chain that will take user input, format the prompt with it, and then send it to the LLM.
from langchain.chains import LLMChain
chain = LLMChain(llm=llm, prompt=prompt)
# Run the chain only specifying the input variable.
print(chain.run("colorful socks"))
Colorful Toes Co.


print(chain.run("colorful socks"))
Colorful Toes Co.
If there are multiple variables, you can input them all at once using a dictionary.
prompt = PromptTemplate(
    input_variables=["company", "product"],
    template="What is a good name for {company} that makes {product}?",
)
chain = LLMChain(llm=llm, prompt=prompt)
print(chain.run({
    'company': "ABC Startup",
    'product': "colorful socks"
    }))
Socktopia Colourful Creations.
You can use a chat model in an LLMChain as well:
from langchain.chat_models import ChatOpenAI
from langchain.prompts.chat import (
    ChatPromptTemplate,
    HumanMessagePromptTemplate,
)
human_message_prompt = HumanMessagePromptTemplate(
        prompt=PromptTemplate(
            template="What is a good name for a company that makes {product}?",
            input_variables=["product"],
        )
    )
chat_prompt_template = ChatPromptTemplate.from_messages([human_message_prompt])
chat = ChatOpenAI(temperature=0.9)
chain = LLMChain(llm=chat, prompt=chat_prompt_template)
print(chain.run("colorful socks"))
Rainbow Socks Co.
Different ways of calling chains#
All classes inherited from Chain offer a few ways of running chain logic. The most direct one is by using __call__:
chat = ChatOpenAI(temperature=0)
prompt_template = "Tell me a {adjective} joke"
llm_chain = LLMChain(
    llm=chat,
    prompt=PromptTemplate.from_template(prompt_template)
)
llm_chain(inputs={"adjective":"corny"})
{'adjective': 'corny',


{'adjective': 'corny',
 'text': 'Why did the tomato turn red? Because it saw the salad dressing!'}
By default, __call__ returns both the input and output key values. You can configure it to only return output key values by setting return_only_outputs to True.
llm_chain("corny", return_only_outputs=True)
{'text': 'Why did the tomato turn red? Because it saw the salad dressing!'}
If the Chain only outputs one output key (i.e. only has one element in its output_keys), you can  use run method. Note that run outputs a string instead of a dictionary.
# llm_chain only has one output key, so we can use run
llm_chain.output_keys
['text']
llm_chain.run({"adjective":"corny"})
'Why did the tomato turn red? Because it saw the salad dressing!'
In the case of one input key, you can input the string directly without specifying the input mapping.
# These two are equivalent
llm_chain.run({"adjective":"corny"})
llm_chain.run("corny")
# These two are also equivalent
llm_chain("corny")
llm_chain({"adjective":"corny"})
{'adjective': 'corny',
 'text': 'Why did the tomato turn red? Because it saw the salad dressing!'}
Tips: You can easily integrate a Chain object as a Tool in your Agent via its run method. See an example here.
Add memory to chains#
Chain supports taking a BaseMemory object as its memory argument, allowing Chain object to persist data across multiple calls. In other words, it makes Chain a stateful object.
from langchain.chains import ConversationChain
from langchain.memory import ConversationBufferMemory
conversation = ConversationChain(
    llm=chat,
    memory=ConversationBufferMemory()


llm=chat,
    memory=ConversationBufferMemory()
)
conversation.run("Answer briefly. What are the first 3 colors of a rainbow?")
# -> The first three colors of a rainbow are red, orange, and yellow.
conversation.run("And the next 4?")
# -> The next four colors of a rainbow are green, blue, indigo, and violet.
'The next four colors of a rainbow are green, blue, indigo, and violet.'
Essentially, BaseMemory defines an interface of how langchain stores memory. It allows reading of stored data through load_memory_variables method and storing new data through save_context method. You can learn more about it in Memory section.
Debug Chain#
It can be hard to debug Chain object solely from its output as most Chain objects involve a fair amount of input prompt preprocessing and LLM output post-processing. Setting verbose to True will print out some internal states of the Chain object while it is being ran.
conversation = ConversationChain(
    llm=chat,
    memory=ConversationBufferMemory(),
    verbose=True
)
conversation.run("What is ChatGPT?")
> Entering new ConversationChain chain...
Prompt after formatting:
The following is a friendly conversation between a human and an AI. The AI is talkative and provides lots of specific details from its context. If the AI does not know the answer to a question, it truthfully says it does not know.
Current conversation:
Human: What is ChatGPT?
AI:
> Finished chain.


Human: What is ChatGPT?
AI:
> Finished chain.
'ChatGPT is an AI language model developed by OpenAI. It is based on the GPT-3 architecture and is capable of generating human-like responses to text prompts. ChatGPT has been trained on a massive amount of text data and can understand and respond to a wide range of topics. It is often used for chatbots, virtual assistants, and other conversational AI applications.'
Combine chains with the SequentialChain#
The next step after calling a language model is to make a series of calls to a language model. We can do this using sequential chains, which are chains that execute their links in a predefined order. Specifically, we will use the SimpleSequentialChain. This is the simplest type of a sequential chain, where each step has a single input/output, and the output of one step is the input to the next.
In this tutorial, our sequential chain will:
First, create a company name for a product. We will reuse the LLMChain we’d previously initialized to create this company name.
Then, create a catchphrase for the product. We will initialize a new LLMChain to create this catchphrase, as shown below.
second_prompt = PromptTemplate(
    input_variables=["company_name"],
    template="Write a catchphrase for the following company: {company_name}",
)
chain_two = LLMChain(llm=llm, prompt=second_prompt)
Now we can combine the two LLMChains, so that we can create a company name and a catchphrase in a single step.
from langchain.chains import SimpleSequentialChain
overall_chain = SimpleSequentialChain(chains=[chain, chain_two], verbose=True)
# Run the chain specifying only the input variable for the first chain.
catchphrase = overall_chain.run("colorful socks")
print(catchphrase)


catchphrase = overall_chain.run("colorful socks")
print(catchphrase)
> Entering new SimpleSequentialChain chain...
Rainbow Socks Co.
"Put a little rainbow in your step!"
> Finished chain.
"Put a little rainbow in your step!"
Create a custom chain with the Chain class#
LangChain provides many chains out of the box, but sometimes you may want to create a custom chain for your specific use case. For this example, we will create a custom chain that concatenates the outputs of 2 LLMChains.
In order to create a custom chain:
Start by subclassing the Chain class,
Fill out the input_keys and output_keys properties,
Add the _call method that shows how to execute the chain.
These steps are demonstrated in the example below:
from langchain.chains import LLMChain
from langchain.chains.base import Chain
from typing import Dict, List
class ConcatenateChain(Chain):
    chain_1: LLMChain
    chain_2: LLMChain
    @property
    def input_keys(self) -> List[str]:
        # Union of the input keys of the two chains.
        all_input_vars = set(self.chain_1.input_keys).union(set(self.chain_2.input_keys))
        return list(all_input_vars)
    @property
    def output_keys(self) -> List[str]:
        return ['concat_output']
    def _call(self, inputs: Dict[str, str]) -> Dict[str, str]:
        output_1 = self.chain_1.run(inputs)
        output_2 = self.chain_2.run(inputs)
        return {'concat_output': output_1 + output_2}
Now, we can try running the chain that we called.
prompt_1 = PromptTemplate(
    input_variables=["product"],


prompt_1 = PromptTemplate(
    input_variables=["product"],
    template="What is a good name for a company that makes {product}?",
)
chain_1 = LLMChain(llm=llm, prompt=prompt_1)
prompt_2 = PromptTemplate(
    input_variables=["product"],
    template="What is a good slogan for a company that makes {product}?",
)
chain_2 = LLMChain(llm=llm, prompt=prompt_2)
concat_chain = ConcatenateChain(chain_1=chain_1, chain_2=chain_2)
concat_output = concat_chain.run("colorful socks")
print(f"Concatenated output:\n{concat_output}")
Concatenated output:
Funky Footwear Company
"Brighten Up Your Day with Our Colorful Socks!"
That’s it! For more details about how to do cool things with Chains, check out the how-to guide for chains.
previous
Chains
next
How-To Guides
 Contents

Why do we need chains?
Quick start: Using LLMChain
Different ways of calling chains
Add memory to chains
Debug Chain
Combine chains with the SequentialChain
Create a custom chain with the Chain class
By Harrison Chase

      © Copyright 2023, Harrison Chase.

  Last updated on Jun 16, 2023.


.ipynb
.pdf
Serialization
 Contents
Saving a chain to disk
Loading a chain from disk
Saving components separately
Serialization#
This notebook covers how to serialize chains to and from disk. The serialization format we use is json or yaml. Currently, only some chains support this type of serialization. We will grow the number of supported chains over time.
Saving a chain to disk#
First, let’s go over how to save a chain to disk. This can be done with the .save method, and specifying a file path with a json or yaml extension.
from langchain import PromptTemplate, OpenAI, LLMChain
template = """Question: {question}
Answer: Let's think step by step."""
prompt = PromptTemplate(template=template, input_variables=["question"])
llm_chain = LLMChain(prompt=prompt, llm=OpenAI(temperature=0), verbose=True)
llm_chain.save("llm_chain.json")
Let’s now take a look at what’s inside this saved file
!cat llm_chain.json
{
    "memory": null,
    "verbose": true,
    "prompt": {
        "input_variables": [
            "question"
        ],
        "output_parser": null,
        "template": "Question: {question}\n\nAnswer: Let's think step by step.",
        "template_format": "f-string"
    },
    "llm": {
        "model_name": "text-davinci-003",
        "temperature": 0.0,
        "max_tokens": 256,
        "top_p": 1,
        "frequency_penalty": 0,
        "presence_penalty": 0,
        "n": 1,
        "best_of": 1,
        "request_timeout": null,


"best_of": 1,
        "request_timeout": null,
        "logit_bias": {},
        "_type": "openai"
    },
    "output_key": "text",
    "_type": "llm_chain"
}
Loading a chain from disk#
We can load a chain from disk by using the load_chain method.
from langchain.chains import load_chain
chain = load_chain("llm_chain.json")
chain.run("whats 2 + 2")
> Entering new LLMChain chain...
Prompt after formatting:
Question: whats 2 + 2
Answer: Let's think step by step.
> Finished chain.
' 2 + 2 = 4'
Saving components separately#
In the above example, we can see that the prompt and llm configuration information is saved in the same json as the overall chain. Alternatively, we can split them up and save them separately. This is often useful to make the saved components more modular. In order to do this, we just need to specify llm_path instead of the llm component, and prompt_path instead of the prompt component.
llm_chain.prompt.save("prompt.json")
!cat prompt.json
{
    "input_variables": [
        "question"
    ],
    "output_parser": null,
    "template": "Question: {question}\n\nAnswer: Let's think step by step.",
    "template_format": "f-string"
}
llm_chain.llm.save("llm.json")
!cat llm.json
{
    "model_name": "text-davinci-003",
    "temperature": 0.0,
    "max_tokens": 256,
    "top_p": 1,
    "frequency_penalty": 0,


"top_p": 1,
    "frequency_penalty": 0,
    "presence_penalty": 0,
    "n": 1,
    "best_of": 1,
    "request_timeout": null,
    "logit_bias": {},
    "_type": "openai"
}
config = {
    "memory": None,
    "verbose": True,
    "prompt_path": "prompt.json",
    "llm_path": "llm.json",
    "output_key": "text",
    "_type": "llm_chain"
}
import json
with open("llm_chain_separate.json", "w") as f:
    json.dump(config, f, indent=2)
!cat llm_chain_separate.json
{
  "memory": null,
  "verbose": true,
  "prompt_path": "prompt.json",
  "llm_path": "llm.json",
  "output_key": "text",
  "_type": "llm_chain"
}
We can then load it in the same way
chain = load_chain("llm_chain_separate.json")
chain.run("whats 2 + 2")
> Entering new LLMChain chain...
Prompt after formatting:
Question: whats 2 + 2
Answer: Let's think step by step.
> Finished chain.
' 2 + 2 = 4'
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Sequential Chains
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Transformation Chain
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Saving a chain to disk
Loading a chain from disk
Saving components separately
By Harrison Chase

      © Copyright 2023, Harrison Chase.

  Last updated on Jun 16, 2023.


.ipynb
.pdf
Loading from LangChainHub
Loading from LangChainHub#
This notebook covers how to load chains from LangChainHub.
from langchain.chains import load_chain
chain = load_chain("lc://chains/llm-math/chain.json")
chain.run("whats 2 raised to .12")
> Entering new LLMMathChain chain...
whats 2 raised to .12
Answer: 1.0791812460476249
> Finished chain.
'Answer: 1.0791812460476249'
Sometimes chains will require extra arguments that were not serialized with the chain. For example, a chain that does question answering over a vector database will require a vector database.
from langchain.embeddings.openai import OpenAIEmbeddings
from langchain.vectorstores import Chroma
from langchain.text_splitter import CharacterTextSplitter
from langchain import OpenAI, VectorDBQA
from langchain.document_loaders import TextLoader
loader = TextLoader('../../state_of_the_union.txt')
documents = loader.load()
text_splitter = CharacterTextSplitter(chunk_size=1000, chunk_overlap=0)
texts = text_splitter.split_documents(documents)
embeddings = OpenAIEmbeddings()
vectorstore = Chroma.from_documents(texts, embeddings)
Running Chroma using direct local API.
Using DuckDB in-memory for database. Data will be transient.
chain = load_chain("lc://chains/vector-db-qa/stuff/chain.json", vectorstore=vectorstore)
query = "What did the president say about Ketanji Brown Jackson"
chain.run(query)


chain.run(query)
" The president said that Ketanji Brown Jackson is a Circuit Court of Appeals Judge, one of the nation's top legal minds, a former top litigator in private practice, a former federal public defender, has received a broad range of support from the Fraternal Order of Police to former judges appointed by Democrats and Republicans, and will continue Justice Breyer's legacy of excellence."
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Creating a custom Chain
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LLM Chain
By Harrison Chase

      © Copyright 2023, Harrison Chase.

  Last updated on Jun 16, 2023.


.ipynb
.pdf
Router Chains
 Contents
LLMRouterChain
EmbeddingRouterChain
Router Chains#
This notebook demonstrates how to use the RouterChain paradigm to create a chain that dynamically selects the next chain to use for a given input.
Router chains are made up of two components:
The RouterChain itself (responsible for selecting the next chain to call)
destination_chains: chains that the router chain can route to
In this notebook we will focus on the different types of routing chains. We will show these routing chains used in a MultiPromptChain to create a question-answering chain that selects the prompt which is most relevant for a given question, and then answers the question using that prompt.
from langchain.chains.router import MultiPromptChain
from langchain.llms import OpenAI
from langchain.chains import ConversationChain
from langchain.chains.llm import LLMChain
from langchain.prompts import PromptTemplate
physics_template = """You are a very smart physics professor. \
You are great at answering questions about physics in a concise and easy to understand manner. \
When you don't know the answer to a question you admit that you don't know.
Here is a question:
{input}"""
math_template = """You are a very good mathematician. You are great at answering math questions. \
You are so good because you are able to break down hard problems into their component parts, \
answer the component parts, and then put them together to answer the broader question.
Here is a question:
{input}"""
prompt_infos = [
    {
        "name": "physics",
        "description": "Good for answering questions about physics",
        "prompt_template": physics_template
    },
    {
        "name": "math",
        "description": "Good for answering math questions",


"description": "Good for answering math questions",
        "prompt_template": math_template
    }
]
llm = OpenAI()
destination_chains = {}
for p_info in prompt_infos:
    name = p_info["name"]
    prompt_template = p_info["prompt_template"]
    prompt = PromptTemplate(template=prompt_template, input_variables=["input"])
    chain = LLMChain(llm=llm, prompt=prompt)
    destination_chains[name] = chain
default_chain = ConversationChain(llm=llm, output_key="text")
LLMRouterChain#
This chain uses an LLM to determine how to route things.
from langchain.chains.router.llm_router import LLMRouterChain, RouterOutputParser
from langchain.chains.router.multi_prompt_prompt import MULTI_PROMPT_ROUTER_TEMPLATE
destinations = [f"{p['name']}: {p['description']}" for p in prompt_infos]
destinations_str = "\n".join(destinations)
router_template = MULTI_PROMPT_ROUTER_TEMPLATE.format(
    destinations=destinations_str
)
router_prompt = PromptTemplate(
    template=router_template,
    input_variables=["input"],
    output_parser=RouterOutputParser(),
)
router_chain = LLMRouterChain.from_llm(llm, router_prompt)
chain = MultiPromptChain(router_chain=router_chain, destination_chains=destination_chains, default_chain=default_chain, verbose=True)
print(chain.run("What is black body radiation?"))
> Entering new MultiPromptChain chain...
physics: {'input': 'What is black body radiation?'}
> Finished chain.


physics: {'input': 'What is black body radiation?'}
> Finished chain.
Black body radiation is the term used to describe the electromagnetic radiation emitted by a “black body”—an object that absorbs all radiation incident upon it. A black body is an idealized physical body that absorbs all incident electromagnetic radiation, regardless of frequency or angle of incidence. It does not reflect, emit or transmit energy. This type of radiation is the result of the thermal motion of the body's atoms and molecules, and it is emitted at all wavelengths. The spectrum of radiation emitted is described by Planck's law and is known as the black body spectrum.
print(chain.run("What is the first prime number greater than 40 such that one plus the prime number is divisible by 3"))
> Entering new MultiPromptChain chain...
math: {'input': 'What is the first prime number greater than 40 such that one plus the prime number is divisible by 3'}
> Finished chain.
?
The answer is 43. One plus 43 is 44 which is divisible by 3.
print(chain.run("What is the name of the type of cloud that rins"))
> Entering new MultiPromptChain chain...
None: {'input': 'What is the name of the type of cloud that rains?'}
> Finished chain.
 The type of cloud that rains is called a cumulonimbus cloud. It is a tall and dense cloud that is often accompanied by thunder and lightning.
EmbeddingRouterChain#
The EmbeddingRouterChain uses embeddings and similarity to route between destination chains.
from langchain.chains.router.embedding_router import EmbeddingRouterChain
from langchain.embeddings import CohereEmbeddings
from langchain.vectorstores import Chroma
names_and_descriptions = [
    ("physics", ["for questions about physics"]),
    ("math", ["for questions about math"]),
]


("math", ["for questions about math"]),
]
router_chain = EmbeddingRouterChain.from_names_and_descriptions(
    names_and_descriptions, Chroma, CohereEmbeddings(), routing_keys=["input"]
)
Using embedded DuckDB without persistence: data will be transient
chain = MultiPromptChain(router_chain=router_chain, destination_chains=destination_chains, default_chain=default_chain, verbose=True)
print(chain.run("What is black body radiation?"))
> Entering new MultiPromptChain chain...
physics: {'input': 'What is black body radiation?'}
> Finished chain.
Black body radiation is the emission of energy from an idealized physical body (known as a black body) that is in thermal equilibrium with its environment. It is emitted in a characteristic pattern of frequencies known as a black-body spectrum, which depends only on the temperature of the body. The study of black body radiation is an important part of astrophysics and atmospheric physics, as the thermal radiation emitted by stars and planets can often be approximated as black body radiation.
print(chain.run("What is the first prime number greater than 40 such that one plus the prime number is divisible by 3"))
> Entering new MultiPromptChain chain...
math: {'input': 'What is the first prime number greater than 40 such that one plus the prime number is divisible by 3'}
> Finished chain.
?
Answer: The first prime number greater than 40 such that one plus the prime number is divisible by 3 is 43.
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LLM Chain
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Sequential Chains
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LLMRouterChain
EmbeddingRouterChain
By Harrison Chase

      © Copyright 2023, Harrison Chase.

  Last updated on Jun 16, 2023.


.ipynb
.pdf
Creating a custom Chain
Creating a custom Chain#
To implement your own custom chain you can subclass Chain and implement the following methods:
from __future__ import annotations
from typing import Any, Dict, List, Optional
from pydantic import Extra
from langchain.base_language import BaseLanguageModel
from langchain.callbacks.manager import (
    AsyncCallbackManagerForChainRun,
    CallbackManagerForChainRun,
)
from langchain.chains.base import Chain
from langchain.prompts.base import BasePromptTemplate
class MyCustomChain(Chain):
    """
    An example of a custom chain.
    """
    prompt: BasePromptTemplate
    """Prompt object to use."""
    llm: BaseLanguageModel
    output_key: str = "text"  #: :meta private:
    class Config:
        """Configuration for this pydantic object."""
        extra = Extra.forbid
        arbitrary_types_allowed = True
    @property
    def input_keys(self) -> List[str]:
        """Will be whatever keys the prompt expects.
        :meta private:
        """
        return self.prompt.input_variables
    @property
    def output_keys(self) -> List[str]:
        """Will always return text key.
        :meta private:
        """
        return [self.output_key]
    def _call(
        self,
        inputs: Dict[str, Any],
        run_manager: Optional[CallbackManagerForChainRun] = None,
    ) -> Dict[str, str]:
        # Your custom chain logic goes here
        # This is just an example that mimics LLMChain
        prompt_value = self.prompt.format_prompt(**inputs)

        # Whenever you call a language model, or another chain, you should pass


# Whenever you call a language model, or another chain, you should pass
        # a callback manager to it. This allows the inner run to be tracked by
        # any callbacks that are registered on the outer run.
        # You can always obtain a callback manager for this by calling
        # `run_manager.get_child()` as shown below.
        response = self.llm.generate_prompt(
            [prompt_value],
            callbacks=run_manager.get_child() if run_manager else None
        )
        # If you want to log something about this run, you can do so by calling
        # methods on the `run_manager`, as shown below. This will trigger any
        # callbacks that are registered for that event.
        if run_manager:
            run_manager.on_text("Log something about this run")

        return {self.output_key: response.generations[0][0].text}
    async def _acall(
        self,
        inputs: Dict[str, Any],
        run_manager: Optional[AsyncCallbackManagerForChainRun] = None,
    ) -> Dict[str, str]:
        # Your custom chain logic goes here
        # This is just an example that mimics LLMChain
        prompt_value = self.prompt.format_prompt(**inputs)

        # Whenever you call a language model, or another chain, you should pass
        # a callback manager to it. This allows the inner run to be tracked by
        # any callbacks that are registered on the outer run.
        # You can always obtain a callback manager for this by calling
        # `run_manager.get_child()` as shown below.
        response = await self.llm.agenerate_prompt(
            [prompt_value],
            callbacks=run_manager.get_child() if run_manager else None
        )


callbacks=run_manager.get_child() if run_manager else None
        )
        # If you want to log something about this run, you can do so by calling
        # methods on the `run_manager`, as shown below. This will trigger any
        # callbacks that are registered for that event.
        if run_manager:
            await run_manager.on_text("Log something about this run")

        return {self.output_key: response.generations[0][0].text}
    @property
    def _chain_type(self) -> str:
        return "my_custom_chain"
from langchain.callbacks.stdout import StdOutCallbackHandler
from langchain.chat_models.openai import ChatOpenAI
from langchain.prompts.prompt import PromptTemplate
chain = MyCustomChain(
    prompt=PromptTemplate.from_template('tell us a joke about {topic}'),
    llm=ChatOpenAI()
)
chain.run({'topic': 'callbacks'}, callbacks=[StdOutCallbackHandler()])
> Entering new MyCustomChain chain...
Log something about this run
> Finished chain.
'Why did the callback function feel lonely? Because it was always waiting for someone to call it back!'
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Async API for Chain
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Loading from LangChainHub
By Harrison Chase

      © Copyright 2023, Harrison Chase.

  Last updated on Jun 16, 2023.