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::: index
lexical analysis, parser, token
:::
A Python program is read by a *parser*. Input to the parser is a stream of `tokens <token>`{.interpreted-text role="term"}, generated by the *lexical analyzer* (also known as the *tokenizer*). This chapter describes how the lexical analyzer produces these tokens.
The lexical analyzer determines the program text\'s `encoding <encodings>`{.interpreted-text role="ref"} (UTF-8 by default), and decodes the text into `source characters <lexical-source-character>`{.interpreted-text role="ref"}. If the text cannot be decoded, a `SyntaxError`{.interpreted-text role="exc"} is raised.
Next, the lexical analyzer uses the source characters to generate a stream of tokens. The type of a generated token generally depends on the next source character to be processed. Similarly, other special behavior of the analyzer depends on the first source character that hasn\'t yet been processed. The following table gives a quick summary of these source characters, with links to sections that contain more information.
+----------------------------------------------------------------------------------------+----------------------------------------------------------------------------------------------------+
| Character | Next token (or other relevant documentation) |
+========================================================================================+====================================================================================================+
| - space | - `Whitespace <whitespace>`{.interpreted-text role="ref"} |
| - tab | |
| - formfeed | |
+----------------------------------------------------------------------------------------+----------------------------------------------------------------------------------------------------+
| - CR, LF | - `New line <line-structure>`{.interpreted-text role="ref"} |
| | - `Indentation <indentation>`{.interpreted-text role="ref"} |
+----------------------------------------------------------------------------------------+----------------------------------------------------------------------------------------------------+
| - backslash (`\`) | - `Explicit line joining <explicit-joining>`{.interpreted-text role="ref"} |
| | - (Also significant in `string escape sequences <escape-sequences>`{.interpreted-text role="ref"}) |
+----------------------------------------------------------------------------------------+----------------------------------------------------------------------------------------------------+
| - hash (`#`) | - `Comment <comments>`{.interpreted-text role="ref"} |
+----------------------------------------------------------------------------------------+----------------------------------------------------------------------------------------------------+
| - quote (`'`, `"`) | - `String literal <strings>`{.interpreted-text role="ref"} |
+----------------------------------------------------------------------------------------+----------------------------------------------------------------------------------------------------+
| - ASCII letter (`a`-`z`, `A`-`Z`) | - `Name <identifiers>`{.interpreted-text role="ref"} |
| - non-ASCII character | - Prefixed `string or bytes literal <strings>`{.interpreted-text role="ref"} |
+----------------------------------------------------------------------------------------+----------------------------------------------------------------------------------------------------+
| - underscore (`_`) | - `Name <identifiers>`{.interpreted-text role="ref"} |
| | - (Can also be part of `numeric literals <numbers>`{.interpreted-text role="ref"}) |
+----------------------------------------------------------------------------------------+----------------------------------------------------------------------------------------------------+
| - number (`0`-`9`) | - `Numeric literal <numbers>`{.interpreted-text role="ref"} |
+----------------------------------------------------------------------------------------+----------------------------------------------------------------------------------------------------+
| - dot (`.`) | - `Numeric literal <numbers>`{.interpreted-text role="ref"} |
| | - `Operator <operators>`{.interpreted-text role="ref"} |
+----------------------------------------------------------------------------------------+----------------------------------------------------------------------------------------------------+
| - question mark (`?`) | - Error (outside string literals and comments) |
| | |
| - dollar (`$`) | |
| | |
| - .. (the following uses zero-width space characters to render .. a literal backquote) | |
| | |
| > backquote (`` ` ``) | |
| | |
| - control character | |
+----------------------------------------------------------------------------------------+----------------------------------------------------------------------------------------------------+
| - other printing character | - `Operator or delimiter <operators>`{.interpreted-text role="ref"} |
+----------------------------------------------------------------------------------------+----------------------------------------------------------------------------------------------------+
| - end of file | - `End marker <endmarker-token>`{.interpreted-text role="ref"} |
+----------------------------------------------------------------------------------------+----------------------------------------------------------------------------------------------------+
## Line structure
::: index
line structure
:::
A Python program is divided into a number of *logical lines*.
### Logical lines
::: index
logical line, physical line, line joining, NEWLINE token
:::
The end of a logical line is represented by the token `~token.NEWLINE`{.interpreted-text role="data"}. Statements cannot cross logical line boundaries except where `!NEWLINE`{.interpreted-text role="data"} is allowed by the syntax (e.g., between statements in compound statements). A logical line is constructed from one or more *physical lines* by following the `explicit <explicit-joining>`{.interpreted-text role="ref"} or `implicit <implicit-joining>`{.interpreted-text role="ref"} *line joining* rules.
### Physical lines
A physical line is a sequence of characters terminated by one the following end-of-line sequences:
- the Unix form using ASCII LF (linefeed),
- the Windows form using the ASCII sequence CR LF (return followed by linefeed),
- the \'\`Classic Mac OS\`\_\_\' form using the ASCII CR (return) character.
Regardless of platform, each of these sequences is replaced by a single ASCII LF (linefeed) character. (This is done even inside `string literals <strings>`{.interpreted-text role="ref"}.) Each line can use any of the sequences; they do not need to be consistent within a file.
The end of input also serves as an implicit terminator for the final physical line.
Formally:
::: {.grammar-snippet group="python-grammar"}
newline: \<ASCII LF\> \| \<ASCII CR\> \<ASCII LF\> \| \<ASCII CR\>
:::
### Comments
::: index
comment, hash character single: \# (hash); comment
:::
A comment starts with a hash character (`#`) that is not part of a string literal, and ends at the end of the physical line. A comment signifies the end of the logical line unless the implicit line joining rules are invoked. Comments are ignored by the syntax.
### Encoding declarations {#encodings}
::: index
source character set, encoding declarations (source file) single: \# (hash); source encoding declaration
:::
If a comment in the first or second line of the Python script matches the regular expression `coding[=:]\s*([-\w.]+)`, this comment is processed as an encoding declaration; the first group of this expression names the encoding of the source code file. The encoding declaration must appear on a line of its own. If it is the second line, the first line must also be a comment-only line. The recommended forms of an encoding expression are :
# -*- coding: <encoding-name> -*-
which is recognized also by GNU Emacs, and :
# vim:fileencoding=<encoding-name>
which is recognized by Bram Moolenaar\'s VIM.
If no encoding declaration is found, the default encoding is UTF-8. If the implicit or explicit encoding of a file is UTF-8, an initial UTF-8 byte-order mark (`b'\xef\xbb\xbf'`) is ignored rather than being a syntax error.
If an encoding is declared, the encoding name must be recognized by Python (see `standard-encodings`{.interpreted-text role="ref"}). The encoding is used for all lexical analysis, including string literals, comments and identifiers.
::: {#lexical-source-character}
All lexical analysis, including string literals, comments and identifiers, works on Unicode text decoded using the source encoding. Any Unicode code point, except the NUL control character, can appear in Python source.
:::
::: {.grammar-snippet group="python-grammar"}
source_character: \<any Unicode code point, except NUL\>
:::
### Explicit line joining {#explicit-joining}
::: index
physical line, line joining, line continuation, backslash character
:::
Two or more physical lines may be joined into logical lines using backslash characters (`\`), as follows: when a physical line ends in a backslash that is not part of a string literal or comment, it is joined with the following forming a single logical line, deleting the backslash and the following end-of-line character. For example:
if 1900 < year < 2100 and 1 <= month <= 12 \
and 1 <= day <= 31 and 0 <= hour < 24 \
and 0 <= minute < 60 and 0 <= second < 60: # Looks like a valid date
return 1
A line ending in a backslash cannot carry a comment. A backslash does not continue a comment. A backslash does not continue a token except for string literals (i.e., tokens other than string literals cannot be split across physical lines using a backslash). A backslash is illegal elsewhere on a line outside a string literal.
### Implicit line joining {#implicit-joining}
Expressions in parentheses, square brackets or curly braces can be split over more than one physical line without using backslashes. For example:
month_names = ['Januari', 'Februari', 'Maart', # These are the
'April', 'Mei', 'Juni', # Dutch names
'Juli', 'Augustus', 'September', # for the months
'Oktober', 'November', 'December'] # of the year
Implicitly continued lines can carry comments. The indentation of the continuation lines is not important. Blank continuation lines are allowed. There is no NEWLINE token between implicit continuation lines. Implicitly continued lines can also occur within triple-quoted strings (see below); in that case they cannot carry comments.
### Blank lines
::: index
single: blank line
:::
A logical line that contains only spaces, tabs, formfeeds and possibly a comment, is ignored (i.e., no `~token.NEWLINE`{.interpreted-text role="data"} token is generated). During interactive input of statements, handling of a blank line may differ depending on the implementation of the read-eval-print loop. In the standard interactive interpreter, an entirely blank logical line (that is, one containing not even whitespace or a comment) terminates a multi-line statement.
### Indentation
::: index
indentation, leading whitespace, space, tab, grouping, statement grouping
:::
Leading whitespace (spaces and tabs) at the beginning of a logical line is used to compute the indentation level of the line, which in turn is used to determine the grouping of statements.
Tabs are replaced (from left to right) by one to eight spaces such that the total number of characters up to and including the replacement is a multiple of eight (this is intended to be the same rule as used by Unix). The total number of spaces preceding the first non-blank character then determines the line\'s indentation. Indentation cannot be split over multiple physical lines using backslashes; the whitespace up to the first backslash determines the indentation.
Indentation is rejected as inconsistent if a source file mixes tabs and spaces in a way that makes the meaning dependent on the worth of a tab in spaces; a `TabError`{.interpreted-text role="exc"} is raised in that case.
**Cross-platform compatibility note:** because of the nature of text editors on non-UNIX platforms, it is unwise to use a mixture of spaces and tabs for the indentation in a single source file. It should also be noted that different platforms may explicitly limit the maximum indentation level.
A formfeed character may be present at the start of the line; it will be ignored for the indentation calculations above. Formfeed characters occurring elsewhere in the leading whitespace have an undefined effect (for instance, they may reset the space count to zero).
::: index
INDENT token, DEDENT token
:::
The indentation levels of consecutive lines are used to generate `~token.INDENT`{.interpreted-text role="data"} and `~token.DEDENT`{.interpreted-text role="data"} tokens, using a stack, as follows.
Before the first line of the file is read, a single zero is pushed on the stack; this will never be popped off again. The numbers pushed on the stack will always be strictly increasing from bottom to top. At the beginning of each logical line, the line\'s indentation level is compared to the top of the stack. If it is equal, nothing happens. If it is larger, it is pushed on the stack, and one `!INDENT`{.interpreted-text role="data"} token is generated. If it is smaller, it *must* be one of the numbers occurring on the stack; all numbers on the stack that are larger are popped off, and for each number popped off a `!DEDENT`{.interpreted-text role="data"} token is generated. At the end of the file, a `!DEDENT`{.interpreted-text role="data"} token is generated for each number remaining on the stack that is larger than zero.
Here is an example of a correctly (though confusingly) indented piece of Python code:
def perm(l):
# Compute the list of all permutations of l
if len(l) <= 1:
return [l]
r = []
for i in range(len(l)):
s = l[:i] + l[i+1:]
p = perm(s)
for x in p:
r.append(l[i:i+1] + x)
return r
The following example shows various indentation errors:
def perm(l): # error: first line indented
for i in range(len(l)): # error: not indented
s = l[:i] + l[i+1:]
p = perm(l[:i] + l[i+1:]) # error: unexpected indent
for x in p:
r.append(l[i:i+1] + x)
return r # error: inconsistent dedent
(Actually, the first three errors are detected by the parser; only the last error is found by the lexical analyzer \-\-- the indentation of `return r` does not match a level popped off the stack.)
### Whitespace between tokens {#whitespace}
Except at the beginning of a logical line or in string literals, the whitespace characters space, tab and formfeed can be used interchangeably to separate tokens:
::: {.grammar-snippet group="python-grammar"}
whitespace: \' \' \| tab \| formfeed
:::
Whitespace is needed between two tokens only if their concatenation could otherwise be interpreted as a different token. For example, `ab` is one token, but `a b` is two tokens. However, `+a` and `+ a` both produce two tokens, `+` and `a`, as `+a` is not a valid token.
### End marker {#endmarker-token}
At the end of non-interactive input, the lexical analyzer generates an `~token.ENDMARKER`{.interpreted-text role="data"} token.
## Other tokens
Besides `~token.NEWLINE`{.interpreted-text role="data"}, `~token.INDENT`{.interpreted-text role="data"} and `~token.DEDENT`{.interpreted-text role="data"}, the following categories of tokens exist: *identifiers* and *keywords* (`~token.NAME`{.interpreted-text role="data"}), *literals* (such as `~token.NUMBER`{.interpreted-text role="data"} and `~token.STRING`{.interpreted-text role="data"}), and other symbols (*operators* and *delimiters*, `~token.OP`{.interpreted-text role="data"}). Whitespace characters (other than logical line terminators, discussed earlier) are not tokens, but serve to delimit tokens. Where ambiguity exists, a token comprises the longest possible string that forms a legal token, when read from left to right.
## Names (identifiers and keywords) {#identifiers}
::: index
identifier, name
:::
`~token.NAME`{.interpreted-text role="data"} tokens represent *identifiers*, *keywords*, and *soft keywords*.
Names are composed of the following characters:
- uppercase and lowercase letters (`A-Z` and `a-z`),
- the underscore (`_`),
- digits (`0` through `9`), which cannot appear as the first character, and
- non-ASCII characters. Valid names may only contain \"letter-like\" and \"digit-like\" characters; see `lexical-names-nonascii`{.interpreted-text role="ref"} for details.
Names must contain at least one character, but have no upper length limit. Case is significant.
Formally, names are described by the following lexical definitions:
::: {.grammar-snippet group="python-grammar"}
NAME: [name_start]{.title-ref} [name_continue]{.title-ref}\* name_start: \"a\"\...\"z\" \| \"A\"\...\"Z\" \| \"\_\" \| \<non-ASCII character\> name_continue: name_start \| \"0\"\...\"9\" identifier: \<\`NAME\`, except keywords\>
:::
Note that not all names matched by this grammar are valid; see `lexical-names-nonascii`{.interpreted-text role="ref"} for details.
### Keywords
::: index
single: keyword single: reserved word
:::
The following names are used as reserved words, or *keywords* of the language, and cannot be used as ordinary identifiers. They must be spelled exactly as written here:
``` text
False await else import pass
None break except in raise
True class finally is return
and continue for lambda try
as def from nonlocal while
assert del global not with
async elif if or yield
```
### Soft Keywords
::: index
soft keyword, keyword
:::
::: versionadded
3.10
:::
Some names are only reserved under specific contexts. These are known as *soft keywords*:
- `match`, `case`, and `_`, when used in the `match`{.interpreted-text role="keyword"} statement.
- `type`, when used in the `type`{.interpreted-text role="keyword"} statement.
- `lazy`, when used before an `import`{.interpreted-text role="keyword"} statement.
These syntactically act as keywords in their specific contexts, but this distinction is done at the parser level, not when tokenizing.
As soft keywords, their use in the grammar is possible while still preserving compatibility with existing code that uses these names as identifier names.
::: versionchanged
3.12 `type` is now a soft keyword.
:::
::: versionchanged
next `lazy` is now a soft keyword.
:::
::: index
single: \_, identifiers single: \_\_, identifiers
:::
### Reserved classes of identifiers {#id-classes}
Certain classes of identifiers (besides keywords) have special meanings. These classes are identified by the patterns of leading and trailing underscore characters:
`_*`
: Not imported by `from module import *`.
`_`
: In a `case` pattern within a `match`{.interpreted-text role="keyword"} statement, `_` is a `soft keyword <soft-keywords>`{.interpreted-text role="ref"} that denotes a `wildcard <wildcard-patterns>`{.interpreted-text role="ref"}.
Separately, the interactive interpreter makes the result of the last evaluation available in the variable `_`. (It is stored in the `builtins`{.interpreted-text role="mod"} module, alongside built-in functions like `print`.)
Elsewhere, `_` is a regular identifier. It is often used to name \"special\" items, but it is not special to Python itself.
:::: note
::: title
Note
:::
The name `_` is often used in conjunction with internationalization; refer to the documentation for the `gettext`{.interpreted-text role="mod"} module for more information on this convention.
It is also commonly used for unused variables.
::::
`__*__`
: System-defined names, informally known as \"dunder\" names. These names are defined by the interpreter and its implementation (including the standard library). Current system names are discussed in the `specialnames`{.interpreted-text role="ref"} section and elsewhere. More will likely be defined in future versions of Python. *Any* use of `__*__` names, in any context, that does not follow explicitly documented use, is subject to breakage without warning.
`__*`
: Class-private names. Names in this category, when used within the context of a class definition, are re-written to use a mangled form to help avoid name clashes between \"private\" attributes of base and derived classes. See section `atom-identifiers`{.interpreted-text role="ref"}.
### Non-ASCII characters in names {#lexical-names-nonascii}
Names that contain non-ASCII characters need additional normalization and validation beyond the rules and grammar explained `above <identifiers>`{.interpreted-text role="ref"}. For example, `ř_1`, `蛇`, or `साँप` are valid names, but `r〰2`, `€`, or `🐍` are not.
This section explains the exact rules.
All names are converted into the [normalization form](https://www.unicode.org/reports/tr15/#Norm_Forms) NFKC while parsing. This means that, for example, some typographic variants of characters are converted to their \"basic\" form. For example, `fiⁿₐˡᵢᶻₐᵗᵢᵒₙ` normalizes to `finalization`, so Python treats them as the same name:
>>> fiⁿₐˡᵢᶻₐᵗᵢᵒₙ = 3
>>> finalization
3
:::: note
::: title
Note
:::
Normalization is done at the lexical level only. Run-time functions that take names as *strings* generally do not normalize their arguments. For example, the variable defined above is accessible at run time in the `globals`{.interpreted-text role="func"} dictionary as `globals()["finalization"]` but not `globals()["fiⁿₐˡᵢᶻₐᵗᵢᵒₙ"]`.
::::
Similarly to how ASCII-only names must contain only letters, digits and the underscore, and cannot start with a digit, a valid name must start with a character in the \"letter-like\" set `xid_start`, and the remaining characters must be in the \"letter- and digit-like\" set `xid_continue`.
These sets based on the *XID_Start* and *XID_Continue* sets as defined by the Unicode standard annex [UAX-31](https://www.unicode.org/reports/tr31/). Python\'s `xid_start` additionally includes the underscore (`_`). Note that Python does not necessarily conform to [UAX-31](https://www.unicode.org/reports/tr31/).
A non-normative listing of characters in the *XID_Start* and *XID_Continue* sets as defined by Unicode is available in the [DerivedCoreProperties.txt](https://www.unicode.org/Public/17.0.0/ucd/DerivedCoreProperties.txt) file in the Unicode Character Database. For reference, the construction rules for the `xid_*` sets are given below.
The set `id_start` is defined as the union of:
- Unicode category `<Lu>` - uppercase letters (includes `A` to `Z`)
- Unicode category `<Ll>` - lowercase letters (includes `a` to `z`)
- Unicode category `<Lt>` - titlecase letters
- Unicode category `<Lm>` - modifier letters
- Unicode category `<Lo>` - other letters
- Unicode category `<Nl>` - letter numbers
- {`"_"`} - the underscore
- `<Other_ID_Start>` - an explicit set of characters in [PropList.txt](https://www.unicode.org/Public/17.0.0/ucd/PropList.txt) to support backwards compatibility
The set `xid_start` then closes this set under NFKC normalization, by removing all characters whose normalization is not of the form `id_start id_continue*`.
The set `id_continue` is defined as the union of:
- `id_start` (see above)
- Unicode category `<Nd>` - decimal numbers (includes `0` to `9`)
- Unicode category `<Pc>` - connector punctuations
- Unicode category `<Mn>` - nonspacing marks
- Unicode category `<Mc>` - spacing combining marks
- `<Other_ID_Continue>` - another explicit set of characters in [PropList.txt](https://www.unicode.org/Public/17.0.0/ucd/PropList.txt) to support backwards compatibility
Again, `xid_continue` closes this set under NFKC normalization.
Unicode categories use the version of the Unicode Character Database as included in the `unicodedata`{.interpreted-text role="mod"} module.
::: seealso
- `3131`{.interpreted-text role="pep"} \-- Supporting Non-ASCII Identifiers
- `672`{.interpreted-text role="pep"} \-- Unicode-related Security Considerations for Python
:::
## Literals
::: index
literal, constant
:::
Literals are notations for constant values of some built-in types.
In terms of lexical analysis, Python has `string, bytes <strings>`{.interpreted-text role="ref"} and `numeric <numbers>`{.interpreted-text role="ref"} literals.
Other \"literals\" are lexically denoted using `keywords <keywords>`{.interpreted-text role="ref"} (`None`, `True`, `False`) and the special `ellipsis token <lexical-ellipsis>`{.interpreted-text role="ref"} (`...`).
::: index
string literal, bytes literal, ASCII single: \' (single quote); string literal single: \" (double quote); string literal
:::
## String and Bytes literals {#strings}
String literals are text enclosed in single quotes (`'`) or double quotes (`"`). For example:
``` python
"spam"
'eggs'
```
The quote used to start the literal also terminates it, so a string literal can only contain the other quote (except with escape sequences, see below). For example:
``` python
'Say "Hello", please.'
"Don't do that!"
```
Except for this limitation, the choice of quote character (`'` or `"`) does not affect how the literal is parsed.
Inside a string literal, the backslash (`\`) character introduces an `escape sequence`{.interpreted-text role="dfn"}, which has special meaning depending on the character after the backslash. For example, `\"` denotes the double quote character, and does *not* end the string:
``` pycon
>>> print("Say \"Hello\" to everyone!")
Say "Hello" to everyone!
```
See `escape sequences <escape-sequences>`{.interpreted-text role="ref"} below for a full list of such sequences, and more details.
::: index
triple-quoted string single: \"\"\"; string literal single: \'\'\'; string literal
:::
### Triple-quoted strings
Strings can also be enclosed in matching groups of three single or double quotes. These are generally referred to as `triple-quoted strings`{.interpreted-text role="dfn"}:
"""This is a triple-quoted string."""
In triple-quoted literals, unescaped quotes are allowed (and are retained), except that three unescaped quotes in a row terminate the literal, if they are of the same kind (`'` or `"`) used at the start:
"""This string has "quotes" inside."""
Unescaped newlines are also allowed and retained:
'''This triple-quoted string
continues on the next line.'''
::: index
single: u\'; string literal single: u\"; string literal
:::
### String prefixes
String literals can have an optional `prefix`{.interpreted-text role="dfn"} that influences how the content of the literal is parsed, for example:
``` python
b"data"
f'{result=}'
```
The allowed prefixes are:
- `b`: `Bytes literal <bytes-literal>`{.interpreted-text role="ref"}
- `r`: `Raw string <raw-strings>`{.interpreted-text role="ref"}
- `f`: `Formatted string literal <f-strings>`{.interpreted-text role="ref"} (\"f-string\")
- `t`: `Template string literal <t-strings>`{.interpreted-text role="ref"} (\"t-string\")
- `u`: No effect (allowed for backwards compatibility)
See the linked sections for details on each type.
Prefixes are case-insensitive (for example, \'`B`\' works the same as \'`b`\'). The \'`r`\' prefix can be combined with \'`f`\', \'`t`\' or \'`b`\', so \'`fr`\', \'`rf`\', \'`tr`\', \'`rt`\', \'`br`\', and \'`rb`\' are also valid prefixes.
::: versionadded
3.3 The `'rb'` prefix of raw bytes literals has been added as a synonym of `'br'`.
Support for the unicode legacy literal (`u'value'`) was reintroduced to simplify the maintenance of dual Python 2.x and 3.x codebases. See `414`{.interpreted-text role="pep"} for more information.
:::
### Formal grammar
String literals, except `"f-strings" <f-strings>`{.interpreted-text role="ref"} and `"t-strings" <t-strings>`{.interpreted-text role="ref"}, are described by the following lexical definitions.
These definitions use `negative lookaheads <lexical-lookaheads>`{.interpreted-text role="ref"} (`!`) to indicate that an ending quote ends the literal.
::: {.grammar-snippet group="python-grammar"}
STRING: \[[stringprefix]{.title-ref}\] ([stringcontent]{.title-ref}) stringprefix: \<(\"r\" \| \"u\" \| \"b\" \| \"br\" \| \"rb\"), case-insensitive\> stringcontent: \| \"\'\'\'\" ( !\"\'\'\'\" [longstringitem]{.title-ref})\* \"\'\'\'\" \| \'\"\"\"\' ( !\'\"\"\"\' [longstringitem]{.title-ref})\* \'\"\"\"\' \| \"\'\" ( !\"\'\" [stringitem]{.title-ref})\* \"\'\" \| \'\"\' ( !\'\"\' [stringitem]{.title-ref})\* \'\"\' stringitem: [stringchar]{.title-ref} \| [stringescapeseq]{.title-ref} stringchar: \<any [source_character]{.title-ref}, except backslash and newline\> longstringitem: [stringitem]{.title-ref} \| newline stringescapeseq: \"\" \<any [source_character]{.title-ref}\>
:::
Note that as in all lexical definitions, whitespace is significant. In particular, the prefix (if any) must be immediately followed by the starting quote.
::: index
physical line, escape sequence, Standard C, C single: (backslash); escape sequence single: \\; escape sequence single: a; escape sequence single: b; escape sequence single: f; escape sequence single: n; escape sequence single: r; escape sequence single: t; escape sequence single: v; escape sequence single: x; escape sequence single: N; escape sequence single: u; escape sequence single: U; escape sequence
:::
### Escape sequences
Unless an \'`r`\' or \'`R`\' prefix is present, escape sequences in string and bytes literals are interpreted according to rules similar to those used by Standard C. The recognized escape sequences are:
Escape Sequence Meaning
-------------------------------------------------- ----------------------------------------------------------------------------------------
`\`\<newline\> `string-escape-ignore`{.interpreted-text role="ref"}
`\\` `Backslash <string-escape-escaped-char>`{.interpreted-text role="ref"}
`\'` `Single quote <string-escape-escaped-char>`{.interpreted-text role="ref"}
`\"` `Double quote <string-escape-escaped-char>`{.interpreted-text role="ref"}
`\a` ASCII Bell (BEL)
`\b` ASCII Backspace (BS)
`\f` ASCII Formfeed (FF)
`\n` ASCII Linefeed (LF)
`\r` ASCII Carriage Return (CR)
`\t` ASCII Horizontal Tab (TAB)
`\v` ASCII Vertical Tab (VT)
`\\\\{ooo}`{.interpreted-text role="samp"} `string-escape-oct`{.interpreted-text role="ref"}
`\\x{hh}`{.interpreted-text role="samp"} `string-escape-hex`{.interpreted-text role="ref"}
`\\N\\{{name}\\}`{.interpreted-text role="samp"} `string-escape-named`{.interpreted-text role="ref"}
`\\u{xxxx}`{.interpreted-text role="samp"} `Hexadecimal Unicode character <string-escape-long-hex>`{.interpreted-text role="ref"}
`\\U{xxxxxxxx}`{.interpreted-text role="samp"} `Hexadecimal Unicode character <string-escape-long-hex>`{.interpreted-text role="ref"}
#### Ignored end of line {#string-escape-ignore}
A backslash can be added at the end of a line to ignore the newline:
>>> 'This string will not include \
... backslashes or newline characters.'
'This string will not include backslashes or newline characters.'
The same result can be achieved using `triple-quoted strings <strings>`{.interpreted-text role="ref"}, or parentheses and `string literal concatenation <string-concatenation>`{.interpreted-text role="ref"}.
#### Escaped characters {#string-escape-escaped-char}
To include a backslash in a non-`raw <raw-strings>`{.interpreted-text role="ref"} Python string literal, it must be doubled. The `\\` escape sequence denotes a single backslash character:
>>> print('C:\\Program Files')
C:\Program Files
Similarly, the `\'` and `\"` sequences denote the single and double quote character, respectively:
>>> print('\' and \"')
' and "
#### Octal character {#string-escape-oct}
The sequence `\\\\{ooo}`{.interpreted-text role="samp"} denotes a *character* with the octal (base 8) value *ooo*:
>>> '\120'
'P'
Up to three octal digits (0 through 7) are accepted.
In a bytes literal, *character* means a *byte* with the given value. In a string literal, it means a Unicode character with the given value.
::: versionchanged
3.11 Octal escapes with value larger than `0o377` (255) produce a `DeprecationWarning`{.interpreted-text role="exc"}.
:::
::: versionchanged
3.12 Octal escapes with value larger than `0o377` (255) produce a `SyntaxWarning`{.interpreted-text role="exc"}. In a future Python version they will raise a `SyntaxError`{.interpreted-text role="exc"}.
:::
#### Hexadecimal character {#string-escape-hex}
The sequence `\\x{hh}`{.interpreted-text role="samp"} denotes a *character* with the hex (base 16) value *hh*:
>>> '\x50'
'P'
Unlike in Standard C, exactly two hex digits are required.
In a bytes literal, *character* means a *byte* with the given value. In a string literal, it means a Unicode character with the given value.
#### Named Unicode character {#string-escape-named}
The sequence `\\N\\{{name}\\}`{.interpreted-text role="samp"} denotes a Unicode character with the given *name*:
>>> '\N{LATIN CAPITAL LETTER P}'
'P'
>>> '\N{SNAKE}'
'🐍'
This sequence cannot appear in `bytes literals <bytes-literal>`{.interpreted-text role="ref"}.
::: versionchanged
3.3 Support for [name aliases](https://www.unicode.org/Public/17.0.0/ucd/NameAliases.txt) has been added.
:::
#### Hexadecimal Unicode characters {#string-escape-long-hex}
These sequences `\\u{xxxx}`{.interpreted-text role="samp"} and `\\U{xxxxxxxx}`{.interpreted-text role="samp"} denote the Unicode character with the given hex (base 16) value. Exactly four digits are required for `\u`; exactly eight digits are required for `\U`. The latter can encode any Unicode character.
``` pycon
>>> '\u1234'
'ሴ'
>>> '\U0001f40d'
'🐍'
```
These sequences cannot appear in `bytes literals <bytes-literal>`{.interpreted-text role="ref"}.
::: index
unrecognized escape sequence
:::
#### Unrecognized escape sequences
Unlike in Standard C, all unrecognized escape sequences are left in the string unchanged, that is, *the backslash is left in the result*:
>>> print('\q')
\q
>>> list('\q')
['\\', 'q']
Note that for bytes literals, the escape sequences only recognized in string literals (`\N...`, `\u...`, `\U...`) fall into the category of unrecognized escapes.
::: versionchanged
3.6 Unrecognized escape sequences produce a `DeprecationWarning`{.interpreted-text role="exc"}.
:::
::: versionchanged
3.12 Unrecognized escape sequences produce a `SyntaxWarning`{.interpreted-text role="exc"}. In a future Python version they will raise a `SyntaxError`{.interpreted-text role="exc"}.
:::
::: index
single: b\'; bytes literal single: b\"; bytes literal
:::
### Bytes literals {#bytes-literal}
`Bytes literals`{.interpreted-text role="dfn"} are always prefixed with \'`b`\' or \'`B`\'; they produce an instance of the `bytes`{.interpreted-text role="class"} type instead of the `str`{.interpreted-text role="class"} type. They may only contain ASCII characters; bytes with a numeric value of 128 or greater must be expressed with escape sequences (typically `string-escape-hex`{.interpreted-text role="ref"} or `string-escape-oct`{.interpreted-text role="ref"}):
``` pycon
>>> b'\x89PNG\r\n\x1a\n'
b'\x89PNG\r\n\x1a\n'
>>> list(b'\x89PNG\r\n\x1a\n')
[137, 80, 78, 71, 13, 10, 26, 10]
```
Similarly, a zero byte must be expressed using an escape sequence (typically `\0` or `\x00`).
::: index
single: r\'; raw string literal single: r\"; raw string literal
:::
### Raw string literals {#raw-strings}
Both string and bytes literals may optionally be prefixed with a letter \'`r`\' or \'`R`\'; such constructs are called `raw string literals`{.interpreted-text role="dfn"} and `raw bytes literals`{.interpreted-text role="dfn"} respectively and treat backslashes as literal characters. As a result, in raw string literals, `escape sequences <escape-sequences>`{.interpreted-text role="ref"} are not treated specially:
``` pycon
>>> r'\d{4}-\d{2}-\d{2}'
'\\d{4}-\\d{2}-\\d{2}'
```
Even in a raw literal, quotes can be escaped with a backslash, but the backslash remains in the result; for example, `r"\""` is a valid string literal consisting of two characters: a backslash and a double quote; `r"\"` is not a valid string literal (even a raw string cannot end in an odd number of backslashes). Specifically, *a raw literal cannot end in a single backslash* (since the backslash would escape the following quote character). Note also that a single backslash followed by a newline is interpreted as those two characters as part of the literal, *not* as a line continuation.
::: index
single: formatted string literal single: interpolated string literal single: string; formatted literal single: string; interpolated literal single: f-string single: fstring single: f\'; formatted string literal single: f\"; formatted string literal single: {} (curly brackets); in formatted string literal single: ! (exclamation); in formatted string literal single: : (colon); in formatted string literal single: = (equals); for help in debugging using string literals
:::
### f-strings[]{#f-strings} {#formatted-string-literals}
::: versionadded
3.6
:::
::: versionchanged
3.7 The `await`{.interpreted-text role="keyword"} and `async for`{.interpreted-text role="keyword"} can be used in expressions within f-strings.
:::
::: versionchanged
3.8 Added the debug specifier (`=`)
:::
::: versionchanged
3.12 Many restrictions on expressions within f-strings have been removed. Notably, nested strings, comments, and backslashes are now permitted.
:::
A `formatted string literal`{.interpreted-text role="dfn"} or `f-string`{.interpreted-text role="dfn"} is a string literal that is prefixed with \'`f`\' or \'`F`\'. Unlike other string literals, f-strings do not have a constant value. They may contain *replacement fields* delimited by curly braces `{}`. Replacement fields contain expressions which are evaluated at run time. For example:
>>> who = 'nobody'
>>> nationality = 'Spanish'
>>> f'{who.title()} expects the {nationality} Inquisition!'
'Nobody expects the Spanish Inquisition!'
Any doubled curly braces (`{{` or `}}`) outside replacement fields are replaced with the corresponding single curly brace:
>>> print(f'{{...}}')
{...}
Other characters outside replacement fields are treated like in ordinary string literals. This means that escape sequences are decoded (except when a literal is also marked as a raw string), and newlines are possible in triple-quoted f-strings:
>>> name = 'Galahad'
>>> favorite_color = 'blue'
>>> print(f'{name}:\t{favorite_color}')
Galahad: blue
>>> print(rf"C:\Users\{name}")
C:\Users\Galahad
>>> print(f'''Three shall be the number of the counting
... and the number of the counting shall be three.''')
Three shall be the number of the counting
and the number of the counting shall be three.
Expressions in formatted string literals are treated like regular Python expressions. Each expression is evaluated in the context where the formatted string literal appears, in order from left to right. An empty expression is not allowed, and both `lambda`{.interpreted-text role="keyword"} and assignment expressions `:=` must be surrounded by explicit parentheses:
>>> f'{(half := 1/2)}, {half * 42}'
'0.5, 21.0'
Reusing the outer f-string quoting type inside a replacement field is permitted:
>>> a = dict(x=2)
>>> f"abc {a["x"]} def"
'abc 2 def'
Backslashes are also allowed in replacement fields and are evaluated the same way as in any other context:
>>> a = ["a", "b", "c"]
>>> print(f"List a contains:\n{"\n".join(a)}")
List a contains:
a
b
c
It is possible to nest f-strings:
>>> name = 'world'
>>> f'Repeated:{f' hello {name}' * 3}'
'Repeated: hello world hello world hello world'
Portable Python programs should not use more than 5 levels of nesting.
::: impl-detail
CPython does not limit nesting of f-strings.
:::
Replacement expressions can contain newlines in both single-quoted and triple-quoted f-strings and they can contain comments. Everything that comes after a `#` inside a replacement field is a comment (even closing braces and quotes). This means that replacement fields with comments must be closed in a different line:
``` text
>>> a = 2
>>> f"abc{a # This comment }" continues until the end of the line
... + 3}"
'abc5'
```
After the expression, replacement fields may optionally contain:
- a *debug specifier* \-- an equal sign (`=`), optionally surrounded by whitespace on one or both sides;
- a *conversion specifier* \-- `!s`, `!r` or `!a`; and/or
- a *format specifier* prefixed with a colon (`:`).
See the `Standard Library section on f-strings <stdtypes-fstrings>`{.interpreted-text role="ref"} for details on how these fields are evaluated.
As that section explains, *format specifiers* are passed as the second argument to the `format`{.interpreted-text role="func"} function to format a replacement field value. For example, they can be used to specify a field width and padding characters using the `Format Specification Mini-Language <formatspec>`{.interpreted-text role="ref"}:
>>> number = 14.3
>>> f'{number:20.7f}'
' 14.3000000'
Top-level format specifiers may include nested replacement fields:
>>> field_size = 20
>>> precision = 7
>>> f'{number:{field_size}.{precision}f}'
' 14.3000000'
These nested fields may include their own conversion fields and `format specifiers <formatspec>`{.interpreted-text role="ref"}:
>>> number = 3
>>> f'{number:{field_size}}'
' 3'
>>> f'{number:{field_size:05}}'
'00000000000000000003'
However, these nested fields may not include more deeply nested replacement fields.
Formatted string literals cannot be used as `docstrings <docstring>`{.interpreted-text role="term"}, even if they do not include expressions:
>>> def foo():
... f"Not a docstring"
...
>>> print(foo.__doc__)
None
::: seealso
- `498`{.interpreted-text role="pep"} \-- Literal String Interpolation
- `701`{.interpreted-text role="pep"} \-- Syntactic formalization of f-strings
- `str.format`{.interpreted-text role="meth"}, which uses a related format string mechanism.
:::
### t-strings[]{#t-strings} {#template-string-literals}
::: versionadded
3.14
:::
A `template string literal`{.interpreted-text role="dfn"} or `t-string`{.interpreted-text role="dfn"} is a string literal that is prefixed with \'`t`\' or \'`T`\'. These strings follow the same syntax rules as `formatted string literals <f-strings>`{.interpreted-text role="ref"}. For differences in evaluation rules, see the `Standard Library section on t-strings <stdtypes-tstrings>`{.interpreted-text role="ref"}
### Formal grammar for f-strings
F-strings are handled partly by the `lexical analyzer`{.interpreted-text role="term"}, which produces the tokens `~token.FSTRING_START`{.interpreted-text role="py:data"}, `~token.FSTRING_MIDDLE`{.interpreted-text role="py:data"} and `~token.FSTRING_END`{.interpreted-text role="py:data"}, and partly by the parser, which handles expressions in the replacement field. The exact way the work is split is a CPython implementation detail.
Correspondingly, the f-string grammar is a mix of `lexical and syntactic definitions <notation-lexical-vs-syntactic>`{.interpreted-text role="ref"}.
Whitespace is significant in these situations:
- There may be no whitespace in `~token.FSTRING_START`{.interpreted-text role="py:data"} (between the prefix and quote).
- Whitespace in `~token.FSTRING_MIDDLE`{.interpreted-text role="py:data"} is part of the literal string contents.
- In `fstring_replacement_field`, if `f_debug_specifier` is present, all whitespace after the opening brace until the `f_debug_specifier`, as well as whitespace immediately following `f_debug_specifier`, is retained as part of the expression.
::: impl-detail
The expression is not handled in the tokenization phase; it is retrieved from the source code using locations of the `{` token and the token after `=`.
:::
The `FSTRING_MIDDLE` definition uses `negative lookaheads <lexical-lookaheads>`{.interpreted-text role="ref"} (`!`) to indicate special characters (backslash, newline, `{`, `}`) and sequences (`f_quote`).
::: {.grammar-snippet group="python-grammar"}
fstring: [FSTRING_START]{.title-ref} [fstring_middle]{.title-ref}\* [FSTRING_END]{.title-ref}
FSTRING_START: [fstringprefix]{.title-ref} (\"\'\" \| \'\"\' \| \"\'\'\'\" \| \'\"\"\"\') FSTRING_END: [f_quote]{.title-ref} fstringprefix: \<(\"f\" \| \"fr\" \| \"rf\"), case-insensitive\> f_debug_specifier: \'=\' f_quote: \<the quote character(s) used in FSTRING_START\>
fstring_middle:
: | [fstring_replacement_field]{.title-ref}
| [FSTRING_MIDDLE]{.title-ref}
FSTRING_MIDDLE:
: | (!\"\" !\`newline\` !\'{\' !\'}\' !\`f_quote\`) [source_character]{.title-ref}
| [stringescapeseq]{.title-ref}
| \"{{\"
| \"}}\"
| \<newline, in triple-quoted f-strings only\>
fstring_replacement_field:
: | \'{\' [f_expression]{.title-ref} \[[f_debug_specifier]{.title-ref}\] \[[fstring_conversion]{.title-ref}\] \[[fstring_full_format_spec]{.title-ref}\] \'}\'
fstring_conversion:
: | \"!\" (\"s\" \| \"r\" \| \"a\")
fstring_full_format_spec:
: | \':\' [fstring_format_spec]{.title-ref}\*
fstring_format_spec:
: | [FSTRING_MIDDLE]{.title-ref}
| [fstring_replacement_field]{.title-ref}
f_expression:
: | \',\'.([conditional_expression]{.title-ref} \| \"\*\" [or_expr]{.title-ref})+ \[\",\"\]
| [yield_expression]{.title-ref}
:::
:::: note
::: title
Note
:::
In the above grammar snippet, the `f_quote` and `FSTRING_MIDDLE` rules are context-sensitive \-- they depend on the contents of `FSTRING_START` of the nearest enclosing `fstring`.
Constructing a more traditional formal grammar from this template is left as an exercise for the reader.
::::
The grammar for t-strings is identical to the one for f-strings, with *t* instead of *f* at the beginning of rule and token names and in the prefix.
::: {.grammar-snippet group="python-grammar"}
tstring: TSTRING_START tstring_middle\* TSTRING_END
\<rest of the t-string grammar is omitted; see above\>
:::
## Numeric literals {#numbers}
::: index
number, numeric literal, integer literal floating-point literal, hexadecimal literal octal literal, binary literal, decimal literal, imaginary literal, complex literal
:::
`~token.NUMBER`{.interpreted-text role="data"} tokens represent numeric literals, of which there are three types: integers, floating-point numbers, and imaginary numbers.
::: {.grammar-snippet group="python-grammar"}
NUMBER: [integer]{.title-ref} \| [floatnumber]{.title-ref} \| [imagnumber]{.title-ref}
:::
The numeric value of a numeric literal is the same as if it were passed as a string to the `int`{.interpreted-text role="class"}, `float`{.interpreted-text role="class"} or `complex`{.interpreted-text role="class"} class constructor, respectively. Note that not all valid inputs for those constructors are also valid literals.
Numeric literals do not include a sign; a phrase like `-1` is actually an expression composed of the unary operator \'`-`\' and the literal `1`.
::: index
single: 0b; integer literal single: 0o; integer literal single: 0x; integer literal single: \_ (underscore); in numeric literal
:::
### Integer literals {#integers}
Integer literals denote whole numbers. For example:
7
3
2147483647
There is no limit for the length of integer literals apart from what can be stored in available memory:
7922816251426433759354395033679228162514264337593543950336
Underscores can be used to group digits for enhanced readability, and are ignored for determining the numeric value of the literal. For example, the following literals are equivalent:
100_000_000_000
100000000000
1_00_00_00_00_000
Underscores can only occur between digits. For example, `_123`, `321_`, and `123__321` are *not* valid literals.
Integers can be specified in binary (base 2), octal (base 8), or hexadecimal (base 16) using the prefixes `0b`, `0o` and `0x`, respectively. Hexadecimal digits 10 through 15 are represented by letters `A`-`F`, case-insensitive. For example:
0b100110111
0b_1110_0101
0o177
0o377
0xdeadbeef
0xDead_Beef
An underscore can follow the base specifier. For example, `0x_1f` is a valid literal, but `0_x1f` and `0x__1f` are not.
Leading zeros in a non-zero decimal number are not allowed. For example, `0123` is not a valid literal. This is for disambiguation with C-style octal literals, which Python used before version 3.0.
Formally, integer literals are described by the following lexical definitions:
::: {.grammar-snippet group="python-grammar"}
integer: [decinteger]{.title-ref} \| [bininteger]{.title-ref} \| [octinteger]{.title-ref} \| [hexinteger]{.title-ref} \| [zerointeger]{.title-ref} decinteger: [nonzerodigit]{.title-ref} (\[\"\_\"\] [digit]{.title-ref})\* bininteger: \"0\" (\"b\" \| \"B\") (\[\"\_\"\] [bindigit]{.title-ref})+ octinteger: \"0\" (\"o\" \| \"O\") (\[\"\_\"\] [octdigit]{.title-ref})+ hexinteger: \"0\" (\"x\" \| \"X\") (\[\"\_\"\] [hexdigit]{.title-ref})+ zerointeger: \"0\"+ (\[\"\_\"\] \"0\")\* nonzerodigit: \"1\"\...\"9\" digit: \"0\"\...\"9\" bindigit: \"0\" \| \"1\" octdigit: \"0\"\...\"7\" hexdigit: [digit]{.title-ref} \| \"a\"\...\"f\" \| \"A\"\...\"F\"
:::
::: versionchanged
3.6 Underscores are now allowed for grouping purposes in literals.
:::
::: index
single: . (dot); in numeric literal single: e; in numeric literal single: \_ (underscore); in numeric literal
:::
### Floating-point literals {#floating}
Floating-point (float) literals, such as `3.14` or `1.5`, denote `approximations of real numbers <datamodel-float>`{.interpreted-text role="ref"}.
They consist of *integer* and *fraction* parts, each composed of decimal digits. The parts are separated by a decimal point, `.`:
2.71828
4.0
Unlike in integer literals, leading zeros are allowed. For example, `077.010` is legal, and denotes the same number as `77.01`.
As in integer literals, single underscores may occur between digits to help readability:
96_485.332_123
3.14_15_93
Either of these parts, but not both, can be empty. For example:
10. # (equivalent to 10.0)
.001 # (equivalent to 0.001)
Optionally, the integer and fraction may be followed by an *exponent*: the letter `e` or `E`, followed by an optional sign, `+` or `-`, and a number in the same format as the integer and fraction parts. The `e` or `E` represents \"times ten raised to the power of\":
1.0e3 # (represents 1.0×10³, or 1000.0)
1.166e-5 # (represents 1.166×10⁻⁵, or 0.00001166)
6.02214076e+23 # (represents 6.02214076×10²³, or 602214076000000000000000.)
In floats with only integer and exponent parts, the decimal point may be omitted:
1e3 # (equivalent to 1.e3 and 1.0e3)
0e0 # (equivalent to 0.)
Formally, floating-point literals are described by the following lexical definitions:
::: {.grammar-snippet group="python-grammar"}
floatnumber:
: | [digitpart]{.title-ref} \".\" \[[digitpart]{.title-ref}\] \[[exponent]{.title-ref}\]
| \".\" [digitpart]{.title-ref} \[[exponent]{.title-ref}\]
| [digitpart]{.title-ref} [exponent]{.title-ref}
digitpart: [digit]{.title-ref} (\[\"\_\"\] [digit]{.title-ref})\* exponent: (\"e\" \| \"E\") \[\"+\" \| \"-\"\] [digitpart]{.title-ref}
:::
::: versionchanged
3.6 Underscores are now allowed for grouping purposes in literals.
:::
::: index
single: j; in numeric literal
:::
### Imaginary literals {#imaginary}
Python has `complex number <typesnumeric>`{.interpreted-text role="ref"} objects, but no complex literals. Instead, *imaginary literals* denote complex numbers with a zero real part.
For example, in math, the complex number 3+4.2*i* is written as the real number 3 added to the imaginary number 4.2*i*. Python uses a similar syntax, except the imaginary unit is written as `j` rather than *i*:
3+4.2j
This is an expression composed of the `integer literal <integers>`{.interpreted-text role="ref"} `3`, the `operator <operators>`{.interpreted-text role="ref"} \'`+`\', and the `imaginary literal <imaginary>`{.interpreted-text role="ref"} `4.2j`. Since these are three separate tokens, whitespace is allowed between them:
3 + 4.2j
No whitespace is allowed *within* each token. In particular, the `j` suffix, may not be separated from the number before it.
The number before the `j` has the same syntax as a floating-point literal. Thus, the following are valid imaginary literals:
4.2j
3.14j
10.j
.001j
1e100j
3.14e-10j
3.14_15_93j
Unlike in a floating-point literal the decimal point can be omitted if the imaginary number only has an integer part. The number is still evaluated as a floating-point number, not an integer:
10j
0j
1000000000000000000000000j # equivalent to 1e+24j
The `j` suffix is case-insensitive. That means you can use `J` instead:
3.14J # equivalent to 3.14j
Formally, imaginary literals are described by the following lexical definition:
::: {.grammar-snippet group="python-grammar"}
imagnumber: ([floatnumber]{.title-ref} \| [digitpart]{.title-ref}) (\"j\" \| \"J\")
:::
## Operators and delimiters[]{#operators}[]{#delimiters} {#lexical-ellipsis}
::: index
single: operators single: delimiters
:::
The following grammar defines `operator`{.interpreted-text role="dfn"} and `delimiter`{.interpreted-text role="dfn"} tokens, that is, the generic `~token.OP`{.interpreted-text role="data"} token type. A `list of these tokens and their names <token_operators_delimiters>`{.interpreted-text role="ref"} is also available in the `!token`{.interpreted-text role="mod"} module documentation.
::: {.grammar-snippet group="python-grammar"}
OP:
: | assignment_operator
| bitwise_operator
| comparison_operator
| enclosing_delimiter
| other_delimiter
| arithmetic_operator
| \"\...\"
| other_op
assignment_operator: \"+=\" \| \"-=\" \| \"\*=\" \| \"\*\*=\" \| \"/=\" \| \"//=\" \| \"%=\" \|
: \"&=\" \| \"[\|=\" \|](##SUBST##|=" |) \"\^=\" \| \"\<\<=\" \| \"\>\>=\" \| \"@=\" \| \":=\"
bitwise_operator: \"&\" \| \"[\|\" \|](##SUBST##|" |) \"\^\" \| \"\~\" \| \"\<\<\" \| \"\>\>\" comparison_operator: \"\<=\" \| \"\>=\" \| \"\<\" \| \"\>\" \| \"==\" \| \"!=\" enclosing_delimiter: \"(\" \| \")\" \| \"\[\" \| \"\]\" \| \"{\" \| \"}\" other_delimiter: \",\" \| \":\" \| \"!\" \| \";\" \| \"=\" \| \"-\>\" arithmetic_operator: \"+\" \| \"-\" \| \"\*\*\" \| \"\*\" \| \"//\" \| \"/\" \| \"%\" other_op: \".\" \| \"@\"
:::
:::: note
::: title
Note
:::
Generally, *operators* are used to combine `expressions <expressions>`{.interpreted-text role="ref"}, while *delimiters* serve other purposes. However, there is no clear, formal distinction between the two categories.
Some tokens can serve as either operators or delimiters, depending on usage. For example, `*` is both the multiplication operator and a delimiter used for sequence unpacking, and `@` is both the matrix multiplication and a delimiter that introduces decorators.
For some tokens, the distinction is unclear. For example, some people consider `.`, `(`, and `)` to be delimiters, while others see the `getattr`{.interpreted-text role="py:func"} operator and the function call operator(s).
Some of Python\'s operators, like `and`, `or`, and `not in`, use `keyword <keywords>`{.interpreted-text role="ref"} tokens rather than \"symbols\" (operator tokens).
::::
A sequence of three consecutive periods (`...`) has a special meaning as an `Ellipsis`{.interpreted-text role="py:data"} literal.
|