— Disassembler for Python bytecode

dis
— Disassembler for Python bytecode¶
Source code: Lib/dis.py
The dis
module supports the analysis of CPython bytecode by
disassembling it. The CPython bytecode which this module takes as an input is
defined in the file Include/opcode.h
and used by the compiler and the
interpreter.
CPython implementation detail: Bytecode is an implementation detail of the CPython interpreter. No guarantees are made that bytecode will not be added, removed, or changed between versions of Python. Use of this module should not be considered to work across Python VMs or Python releases.
Changed in version 3.6: Use 2 bytes for each instruction. Previously the number of bytes varied by instruction.
Changed in version 3.10: The argument of jump, exception handling and loop instructions is now the instruction offset rather than the byte offset.
Changed in version 3.11: Some instructions are accompanied by one or more inline cache entries,
which take the form of CACHE
instructions. These instructions
are hidden by default, but can be shown by passing show_caches=True
to
any dis
utility. Furthermore, the interpreter now adapts the
bytecode to specialize it for different runtime conditions. The
adaptive bytecode can be shown by passing adaptive=True
.
Changed in version 3.12: The argument of a jump is the offset of the target instruction relative
to the instruction that appears immediately after the jump instruction’s
CACHE
entries.
As a consequence, the presence of the CACHE
instructions is
transparent for forward jumps but needs to be taken into account when
reasoning about backward jumps.
Changed in version 3.13: The output shows logical labels rather than instruction offsets
for jump targets and exception handlers. The -O
command line
option and the show_offsets
argument were added.
Example: Given the function myfunc()
:
def myfunc(alist):
return len(alist)
the following command can be used to display the disassembly of
myfunc()
:
>>> dis.dis(myfunc)
2 RESUME 0
3 LOAD_GLOBAL 1 (len + NULL)
LOAD_FAST_BORROW 0 (alist)
CALL 1
RETURN_VALUE
(The “2” is a line number).
Command-line interface¶
The dis
module can be invoked as a script from the command line:
python -m dis [-h] [-C] [-O] [-P] [-S] [infile]
The following options are accepted:
- -h, --help¶
Display usage and exit.
- -C, --show-caches¶
Show inline caches.
Added in version 3.13.
- -O, --show-offsets¶
Show offsets of instructions.
Added in version 3.13.
- -P, --show-positions¶
Show positions of instructions in the source code.
Added in version 3.14.
- -S, --specialized¶
Show specialized bytecode.
Added in version 3.14.
If infile
is specified, its disassembled code will be written to stdout.
Otherwise, disassembly is performed on compiled source code received from stdin.
Bytecode analysis¶
Added in version 3.4.
The bytecode analysis API allows pieces of Python code to be wrapped in a
Bytecode
object that provides easy access to details of the compiled
code.
- class dis.Bytecode(x, *, first_line=None, current_offset=None, show_caches=False, adaptive=False, show_offsets=False, show_positions=False)¶
Analyse the bytecode corresponding to a function, generator, asynchronous generator, coroutine, method, string of source code, or a code object (as returned by
compile()
).This is a convenience wrapper around many of the functions listed below, most notably
get_instructions()
, as iterating over aBytecode
instance yields the bytecode operations asInstruction
instances.If first_line is not
None
, it indicates the line number that should be reported for the first source line in the disassembled code. Otherwise, the source line information (if any) is taken directly from the disassembled code object.If current_offset is not
None
, it refers to an instruction offset in the disassembled code. Setting this meansdis()
will display a “current instruction” marker against the specified opcode.If show_caches is
True
,dis()
will display inline cache entries used by the interpreter to specialize the bytecode.If adaptive is
True
,dis()
will display specialized bytecode that may be different from the original bytecode.If show_offsets is
True
,dis()
will include instruction offsets in the output.If show_positions is
True
,dis()
will include instruction source code positions in the output.- classmethod from_traceback(tb, *, show_caches=False)¶
Construct a
Bytecode
instance from the given traceback, setting current_offset to the instruction responsible for the exception.
- codeobj¶
The compiled code object.
- first_line¶
The first source line of the code object (if available)
- dis()¶
Return a formatted view of the bytecode operations (the same as printed by
dis.dis()
, but returned as a multi-line string).
- info()¶
Return a formatted multi-line string with detailed information about the code object, like
code_info()
.
Changed in version 3.7: This can now handle coroutine and asynchronous generator objects.
Changed in version 3.11: Added the show_caches and adaptive parameters.
Changed in version 3.13: Added the show_offsets parameter
Changed in version 3.14: Added the show_positions parameter.
Example:
>>> bytecode = dis.Bytecode(myfunc)
>>> for instr in bytecode:
... print(instr.opname)
...
RESUME
LOAD_GLOBAL
LOAD_FAST_BORROW
CALL
RETURN_VALUE
Analysis functions¶
The dis
module also defines the following analysis functions that convert
the input directly to the desired output. They can be useful if only a single
operation is being performed, so the intermediate analysis object isn’t useful:
- dis.code_info(x)¶
Return a formatted multi-line string with detailed code object information for the supplied function, generator, asynchronous generator, coroutine, method, source code string or code object.
Note that the exact contents of code info strings are highly implementation dependent and they may change arbitrarily across Python VMs or Python releases.
Added in version 3.2.
Changed in version 3.7: This can now handle coroutine and asynchronous generator objects.
- dis.show_code(x, *, file=None)¶
Print detailed code object information for the supplied function, method, source code string or code object to file (or
sys.stdout
if file is not specified).This is a convenient shorthand for
print(code_info(x), file=file)
, intended for interactive exploration at the interpreter prompt.Added in version 3.2.
Changed in version 3.4: Added file parameter.
- dis.dis(x=None, *, file=None, depth=None, show_caches=False, adaptive=False, show_offsets=False, show_positions=False)¶
Disassemble the x object. x can denote either a module, a class, a method, a function, a generator, an asynchronous generator, a coroutine, a code object, a string of source code or a byte sequence of raw bytecode. For a module, it disassembles all functions. For a class, it disassembles all methods (including class and static methods). For a code object or sequence of raw bytecode, it prints one line per bytecode instruction. It also recursively disassembles nested code objects. These can include generator expressions, nested functions, the bodies of nested classes, and the code objects used for annotation scopes. Strings are first compiled to code objects with the
compile()
built-in function before being disassembled. If no object is provided, this function disassembles the last traceback.The disassembly is written as text to the supplied file argument if provided and to
sys.stdout
otherwise.The maximal depth of recursion is limited by depth unless it is
None
.depth=0
means no recursion.If show_caches is
True
, this function will display inline cache entries used by the interpreter to specialize the bytecode.If adaptive is
True
, this function will display specialized bytecode that may be different from the original bytecode.Changed in version 3.4: Added file parameter.
Changed in version 3.7: Implemented recursive disassembling and added depth parameter.
Changed in version 3.7: This can now handle coroutine and asynchronous generator objects.
Changed in version 3.11: Added the show_caches and adaptive parameters.
Changed in version 3.13: Added the show_offsets parameter.
Changed in version 3.14: Added the show_positions parameter.
- dis.distb(tb=None, *, file=None, show_caches=False, adaptive=False, show_offset=False, show_positions=False)¶
Disassemble the top-of-stack function of a traceback, using the last traceback if none was passed. The instruction causing the exception is indicated.
The disassembly is written as text to the supplied file argument if provided and to
sys.stdout
otherwise.Changed in version 3.4: Added file parameter.
Changed in version 3.11: Added the show_caches and adaptive parameters.
Changed in version 3.13: Added the show_offsets parameter.
Changed in version 3.14: Added the show_positions parameter.
- dis.disassemble(code, lasti=-1, *, file=None, show_caches=False, adaptive=False, show_offsets=False, show_positions=False)¶
- dis.disco(code, lasti=-1, *, file=None, show_caches=False, adaptive=False, show_offsets=False, show_positions=False)¶
Disassemble a code object, indicating the last instruction if lasti was provided. The output is divided in the following columns:
the source code location of the instruction. Complete location information is shown if show_positions is true. Otherwise (the default) only the line number is displayed.
the current instruction, indicated as
-->
,a labelled instruction, indicated with
>>
,the address of the instruction,
the operation code name,
operation parameters, and
interpretation of the parameters in parentheses.
The parameter interpretation recognizes local and global variable names, constant values, branch targets, and compare operators.
The disassembly is written as text to the supplied file argument if provided and to
sys.stdout
otherwise.Changed in version 3.4: Added file parameter.
Changed in version 3.11: Added the show_caches and adaptive parameters.
Changed in version 3.13: Added the show_offsets parameter.
Changed in version 3.14: Added the show_positions parameter.
- dis.get_instructions(x, *, first_line=None, show_caches=False, adaptive=False)¶
Return an iterator over the instructions in the supplied function, method, source code string or code object.
The iterator generates a series of
Instruction
named tuples giving the details of each operation in the supplied code.If first_line is not
None
, it indicates the line number that should be reported for the first source line in the disassembled code. Otherwise, the source line information (if any) is taken directly from the disassembled code object.The adaptive parameter works as it does in
dis()
.Added in version 3.4.
Changed in version 3.11: Added the show_caches and adaptive parameters.
Changed in version 3.13: The show_caches parameter is deprecated and has no effect. The iterator generates the
Instruction
instances with the cache_info field populated (regardless of the value of show_caches) and it no longer generates separate items for the cache entries.
- dis.findlinestarts(code)¶
This generator function uses the
co_lines()
method of the code object code to find the offsets which are starts of lines in the source code. They are generated as(offset, lineno)
pairs.Changed in version 3.6: Line numbers can be decreasing. Before, they were always increasing.
Changed in version 3.10: The PEP 626
co_lines()
method is used instead of theco_firstlineno
andco_lnotab
attributes of the code object.Changed in version 3.13: Line numbers can be
None
for bytecode that does not map to source lines.
- dis.findlabels(code)¶
Detect all offsets in the raw compiled bytecode string code which are jump targets, and return a list of these offsets.
- dis.stack_effect(opcode, oparg=None, *, jump=None)¶
Compute the stack effect of opcode with argument oparg.
If the code has a jump target and jump is
True
,stack_effect()
will return the stack effect of jumping. If jump isFalse
, it will return the stack effect of not jumping. And if jump isNone
(default), it will return the maximal stack effect of both cases.Added in version 3.4.
Changed in version 3.8: Added jump parameter.
Changed in version 3.13: If
oparg
is omitted (orNone
), the stack effect is now returned foroparg=0
. Previously this was an error for opcodes that use their arg. It is also no longer an error to pass an integeroparg
when theopcode
does not use it; theoparg
in this case is ignored.
Python Bytecode Instructions¶
The get_instructions()
function and Bytecode
class provide
details of bytecode instructions as Instruction
instances:
- class dis.Instruction¶
Details for a bytecode operation
- opcode¶
numeric code for operation, corresponding to the opcode values listed below and the bytecode values in the Opcode collections.
- opname¶
human readable name for operation
- baseopcode¶
numeric code for the base operation if operation is specialized; otherwise equal to
opcode
- baseopname¶
human readable name for the base operation if operation is specialized; otherwise equal to
opname
- arg¶
numeric argument to operation (if any), otherwise
None
- argval¶
resolved arg value (if any), otherwise
None
- argrepr¶
human readable description of operation argument (if any), otherwise an empty string.
- offset¶
start index of operation within bytecode sequence
- start_offset¶
start index of operation within bytecode sequence, including prefixed
EXTENDED_ARG
operations if present; otherwise equal tooffset
- cache_offset¶
start index of the cache entries following the operation
- end_offset¶
end index of the cache entries following the operation
- starts_line¶
True
if this opcode starts a source line, otherwiseFalse
- line_number¶
source line number associated with this opcode (if any), otherwise
None
- is_jump_target¶
True
if other code jumps to here, otherwiseFalse
- jump_target¶
bytecode index of the jump target if this is a jump operation, otherwise
None
- positions¶
dis.Positions
object holding the start and end locations that are covered by this instruction.
- cache_info¶
Information about the cache entries of this instruction, as triplets of the form
(name, size, data)
, where thename
andsize
describe the cache format and data is the contents of the cache.cache_info
isNone
if the instruction does not have caches.
Added in version 3.4.
Changed in version 3.11: Field
positions
is added.Changed in version 3.13: Changed field
starts_line
.Added fields
start_offset
,cache_offset
,end_offset
,baseopname
,baseopcode
,jump_target
,oparg
,line_number
andcache_info
.
- class dis.Positions¶
In case the information is not available, some fields might be
None
.- lineno¶
- end_lineno¶
- col_offset¶
- end_col_offset¶
Added in version 3.11.
The Python compiler currently generates the following bytecode instructions.
General instructions
In the following, We will refer to the interpreter stack as STACK
and describe
operations on it as if it was a Python list. The top of the stack corresponds to
STACK[-1]
in this language.
- NOP¶
Do nothing code. Used as a placeholder by the bytecode optimizer, and to generate line tracing events.
- NOT_TAKEN¶
Do nothing code. Used by the interpreter to record
BRANCH_LEFT
andBRANCH_RIGHT
events forsys.monitoring
.Added in version 3.14.
- POP_ITER¶
Removes the iterator from the top of the stack.
Added in version 3.14.
- POP_TOP¶
Removes the top-of-stack item:
STACK.pop()
- END_FOR¶
Removes the top-of-stack item. Equivalent to
POP_TOP
. Used to clean up at the end of loops, hence the name.Added in version 3.12.
- END_SEND¶
Implements
del STACK[-2]
. Used to clean up when a generator exits.Added in version 3.12.
- COPY(i)¶
Push the i-th item to the top of the stack without removing it from its original location:
assert i > 0 STACK.append(STACK[-i])
Added in version 3.11.
- SWAP(i)¶
Swap the top of the stack with the i-th element:
STACK[-i], STACK[-1] = STACK[-1], STACK[-i]
Added in version 3.11.
- CACHE¶
Rather than being an actual instruction, this opcode is used to mark extra space for the interpreter to cache useful data directly in the bytecode itself. It is automatically hidden by all
dis
utilities, but can be viewed withshow_caches=True
.Logically, this space is part of the preceding instruction. Many opcodes expect to be followed by an exact number of caches, and will instruct the interpreter to skip over them at runtime.
Populated caches can look like arbitrary instructions, so great care should be taken when reading or modifying raw, adaptive bytecode containing quickened data.
Added in version 3.11.
Unary operations
Unary operations take the top of the stack, apply the operation, and push the result back on the stack.
- UNARY_NEGATIVE¶
Implements
STACK[-1] = -STACK[-1]
.
- UNARY_NOT¶
Implements
STACK[-1] = not STACK[-1]
.Changed in version 3.13: This instruction now requires an exact
bool
operand.
- UNARY_INVERT¶
Implements
STACK[-1] = ~STACK[-1]
.
- GET_ITER¶
Implements
STACK[-1] = iter(STACK[-1])
.
- GET_YIELD_FROM_ITER¶
If
STACK[-1]
is a generator iterator or coroutine object it is left as is. Otherwise, implementsSTACK[-1] = iter(STACK[-1])
.Added in version 3.5.
- TO_BOOL¶
Implements
STACK[-1] = bool(STACK[-1])
.Added in version 3.13.
Binary and in-place operations
Binary operations remove the top two items from the stack (STACK[-1]
and
STACK[-2]
). They perform the operation, then put the result back on the stack.
In-place operations are like binary operations, but the operation is done in-place
when STACK[-2]
supports it, and the resulting STACK[-1]
may be (but does
not have to be) the original STACK[-2]
.
- BINARY_OP(op)¶
Implements the binary and in-place operators (depending on the value of op):
rhs = STACK.pop() lhs = STACK.pop() STACK.append(lhs op rhs)
Added in version 3.11.
Changed in version 3.14: With oparg :
NB_SUBSCR
, implements binary subscript (replaces opcodeBINARY_SUBSCR
)
- STORE_SUBSCR¶
Implements:
key = STACK.pop() container = STACK.pop() value = STACK.pop() container[key] = value
- DELETE_SUBSCR¶
Implements:
key = STACK.pop() container = STACK.pop() del container[key]
- BINARY_SLICE¶
Implements:
end = STACK.pop() start = STACK.pop() container = STACK.pop() STACK.append(container[start:end])
Added in version 3.12.
- STORE_SLICE¶
Implements:
end = STACK.pop() start = STACK.pop() container = STACK.pop() value = STACK.pop() container[start:end] = value
Added in version 3.12.
Coroutine opcodes
- GET_AWAITABLE(where)¶
Implements
STACK[-1] = get_awaitable(STACK[-1])
, whereget_awaitable(o)
returnso
ifo
is a coroutine object or a generator object with theCO_ITERABLE_COROUTINE
flag, or resolveso.__await__
.If the
where
operand is nonzero, it indicates where the instruction occurs:1
: After a call to__aenter__
2
: After a call to__aexit__
Added in version 3.5.
Changed in version 3.11: Previously, this instruction did not have an oparg.
- GET_AITER¶
Implements
STACK[-1] = STACK[-1].__aiter__()
.Added in version 3.5.
Changed in version 3.7: Returning awaitable objects from
__aiter__
is no longer supported.
- GET_ANEXT¶
Implement
STACK.append(get_awaitable(STACK[-1].__anext__()))
to the stack. SeeGET_AWAITABLE
for details aboutget_awaitable
.Added in version 3.5.
- END_ASYNC_FOR¶
Terminates an
async for
loop. Handles an exception raised when awaiting a next item. The stack contains the async iterable inSTACK[-2]
and the raised exception inSTACK[-1]
. Both are popped. If the exception is notStopAsyncIteration
, it is re-raised.Added in version 3.8.
Changed in version 3.11: Exception representation on the stack now consist of one, not three, items.
- CLEANUP_THROW¶
Handles an exception raised during a
throw()
orclose()
call through the current frame. IfSTACK[-1]
is an instance ofStopIteration
, pop three values from the stack and push itsvalue
member. Otherwise, re-raiseSTACK[-1]
.Added in version 3.12.
Miscellaneous opcodes
- SET_ADD(i)¶
Implements:
item = STACK.pop() set.add(STACK[-i], item)
Used to implement set comprehensions.
- LIST_APPEND(i)¶
Implements:
item = STACK.pop() list.append(STACK[-i], item)
Used to implement list comprehensions.
- MAP_ADD(i)¶
Implements:
value = STACK.pop() key = STACK.pop() dict.__setitem__(STACK[-i], key, value)
Used to implement dict comprehensions.
Added in version 3.1.
Changed in version 3.8: Map value is
STACK[-1]
and map key isSTACK[-2]
. Before, those were reversed.
For all of the SET_ADD
, LIST_APPEND
and MAP_ADD
instructions, while the added value or key/value pair is popped off, the
container object remains on the stack so that it is available for further
iterations of the loop.
- RETURN_VALUE¶
Returns with
STACK[-1]
to the caller of the function.
- YIELD_VALUE¶
Yields
STACK.pop()
from a generator.Changed in version 3.11: oparg set to be the stack depth.
Changed in version 3.12: oparg set to be the exception block depth, for efficient closing of generators.
Changed in version 3.13: oparg is
1
if this instruction is part of a yield-from or await, and0
otherwise.
- SETUP_ANNOTATIONS¶
Checks whether
__annotations__
is defined inlocals()
, if not it is set up to an emptydict
. This opcode is only emitted if a class or module body contains variable annotations statically.Added in version 3.6.
- POP_EXCEPT¶
Pops a value from the stack, which is used to restore the exception state.
Changed in version 3.11: Exception representation on the stack now consist of one, not three, items.
- RERAISE¶
Re-raises the exception currently on top of the stack. If oparg is non-zero, pops an additional value from the stack which is used to set
f_lasti
of the current frame.Added in version 3.9.
Changed in version 3.11: Exception representation on the stack now consist of one, not three, items.
- PUSH_EXC_INFO¶
Pops a value from the stack. Pushes the current exception to the top of the stack. Pushes the value originally popped back to the stack. Used in exception handlers.
Added in version 3.11.
- CHECK_EXC_MATCH¶
Performs exception matching for
except
. Tests whether theSTACK[-2]
is an exception matchingSTACK[-1]
. PopsSTACK[-1]
and pushes the boolean result of the test.Added in version 3.11.
- CHECK_EG_MATCH¶
Performs exception matching for
except*
. Appliessplit(STACK[-1])
on the exception group representingSTACK[-2]
.In case of a match, pops two items from the stack and pushes the non-matching subgroup (
None
in case of full match) followed by the matching subgroup. When there is no match, pops one item (the match type) and pushesNone
.Added in version 3.11.
- WITH_EXCEPT_START¶
Calls the function in position 4 on the stack with arguments (type, val, tb) representing the exception at the top of the stack. Used to implement the call
context_manager.__exit__(*exc_info())
when an exception has occurred in awith
statement.Added in version 3.9.
Changed in version 3.11: The
__exit__
function is in position 4 of the stack rather than 7. Exception representation on the stack now consist of one, not three, items.
- LOAD_COMMON_CONSTANT¶
Pushes a common constant onto the stack. The interpreter contains a hardcoded list of constants supported by this instruction. Used by the
assert
statement to loadAssertionError
.Added in version 3.14.
- LOAD_BUILD_CLASS¶
Pushes
builtins.__build_class__()
onto the stack. It is later called to construct a class.
- GET_LEN¶
Perform
STACK.append(len(STACK[-1]))
. Used inmatch
statements where comparison with structure of pattern is needed.Added in version 3.10.
- MATCH_MAPPING¶
If
STACK[-1]
is an instance ofcollections.abc.Mapping
(or, more technically: if it has thePy_TPFLAGS_MAPPING
flag set in itstp_flags
), pushTrue
onto the stack. Otherwise, pushFalse
.Added in version 3.10.
- MATCH_SEQUENCE¶
If
STACK[-1]
is an instance ofcollections.abc.Sequence
and is not an instance ofstr
/bytes
/bytearray
(or, more technically: if it has thePy_TPFLAGS_SEQUENCE
flag set in itstp_flags
), pushTrue
onto the stack. Otherwise, pushFalse
.Added in version 3.10.
- MATCH_KEYS¶
STACK[-1]
is a tuple of mapping keys, andSTACK[-2]
is the match subject. IfSTACK[-2]
contains all of the keys inSTACK[-1]
, push atuple
containing the corresponding values. Otherwise, pushNone
.Added in version 3.10.
Changed in version 3.11: Previously, this instruction also pushed a boolean value indicating success (
True
) or failure (False
).
- STORE_NAME(namei)¶
Implements
name = STACK.pop()
. namei is the index of name in the attributeco_names
of the code object. The compiler tries to useSTORE_FAST
orSTORE_GLOBAL
if possible.
- DELETE_NAME(namei)¶
Implements
del name
, where namei is the index intoco_names
attribute of the code object.
- UNPACK_SEQUENCE(count)¶
Unpacks
STACK[-1]
into count individual values, which are put onto the stack right-to-left. Require there to be exactly count values.:assert(len(STACK[-1]) == count) STACK.extend(STACK.pop()[:-count-1:-1])
- UNPACK_EX(counts)¶
Implements assignment with a starred target: Unpacks an iterable in
STACK[-1]
into individual values, where the total number of values can be smaller than the number of items in the iterable: one of the new values will be a list of all leftover items.The number of values before and after the list value is limited to 255.
The number of values before the list value is encoded in the argument of the opcode. The number of values after the list if any is encoded using an
EXTENDED_ARG
. As a consequence, the argument can be seen as a two bytes values where the low byte of counts is the number of values before the list value, the high byte of counts the number of values after it.The extracted values are put onto the stack right-to-left, i.e.
a, *b, c = d
will be stored after execution asSTACK.extend((a, b, c))
.
- STORE_ATTR(namei)¶
Implements:
obj = STACK.pop() value = STACK.pop() obj.name = value
where namei is the index of name in
co_names
of the code object.
- DELETE_ATTR(namei)¶
Implements:
obj = STACK.pop() del obj.name
where namei is the index of name into
co_names
of the code object.
- STORE_GLOBAL(namei)¶
Works as
STORE_NAME
, but stores the name as a global.
- DELETE_GLOBAL(namei)¶
Works as
DELETE_NAME
, but deletes a global name.
- LOAD_CONST(consti)¶
Pushes
co_consts[consti]
onto the stack.
- LOAD_SMALL_INT(i)¶
Pushes the integer
i
onto the stack.i
must be inrange(256)
Added in version 3.14.
- LOAD_NAME(namei)¶
Pushes the value associated with
co_names[namei]
onto the stack. The name is looked up within the locals, then the globals, then the builtins.
- LOAD_LOCALS¶
Pushes a reference to the locals dictionary onto the stack. This is used to prepare namespace dictionaries for
LOAD_FROM_DICT_OR_DEREF
andLOAD_FROM_DICT_OR_GLOBALS
.Added in version 3.12.
- LOAD_FROM_DICT_OR_GLOBALS(i)¶
Pops a mapping off the stack and looks up the value for
co_names[namei]
. If the name is not found there, looks it up in the globals and then the builtins, similar toLOAD_GLOBAL
. This is used for loading global variables in annotation scopes within class bodies.Added in version 3.12.
- BUILD_TEMPLATE¶
Constructs a new
Template
instance from a tuple of strings and a tuple of interpolations and pushes the resulting object onto the stack:interpolations = STACK.pop() strings = STACK.pop() STACK.append(_build_template(strings, interpolations))
Added in version 3.14.
- BUILD_INTERPOLATION(format)¶
Constructs a new
Interpolation
instance from a value and its source expression and pushes the resulting object onto the stack.If no conversion or format specification is present,
format
is set to2
.If the low bit of
format
is set, it indicates that the interpolation contains a format specification.If
format >> 2
is non-zero, it indicates that the interpolation contains a conversion. The value offormat >> 2
is the conversion type (0
for no conversion,1
for!s
,2
for!r
, and3
for!a
):conversion = format >> 2 if format & 1: format_spec = STACK.pop() else: format_spec = None expression = STACK.pop() value = STACK.pop() STACK.append(_build_interpolation(value, expression, conversion, format_spec))
Added in version 3.14.
- BUILD_TUPLE(count)¶
Creates a tuple consuming count items from the stack, and pushes the resulting tuple onto the stack:
if count == 0: value = () else: value = tuple(STACK[-count:]) STACK = STACK[:-count] STACK.append(value)
- BUILD_LIST(count)¶
Works as
BUILD_TUPLE
, but creates a list.
- BUILD_SET(count)¶
Works as
BUILD_TUPLE
, but creates a set.
- BUILD_MAP(count)¶
Pushes a new dictionary object onto the stack. Pops
2 * count
items so that the dictionary holds count entries:{..., STACK[-4]: STACK[-3], STACK[-2]: STACK[-1]}
.Changed in version 3.5: The dictionary is created from stack items instead of creating an empty dictionary pre-sized to hold count items.
- BUILD_STRING(count)¶
Concatenates count strings from the stack and pushes the resulting string onto the stack.
Added in version 3.6.
- LIST_EXTEND(i)¶
Implements:
seq = STACK.pop() list.extend(STACK[-i], seq)
Used to build lists.
Added in version 3.9.
- SET_UPDATE(i)¶
Implements:
seq = STACK.pop() set.update(STACK[-i], seq)
Used to build sets.
Added in version 3.9.
- DICT_UPDATE(i)¶
Implements:
map = STACK.pop() dict.update(STACK[-i], map)
Used to build dicts.
Added in version 3.9.
- DICT_MERGE(i)¶
Like
DICT_UPDATE
but raises an exception for duplicate keys.Added in version 3.9.
- LOAD_ATTR(namei)¶
If the low bit of
namei
is not set, this replacesSTACK[-1]
withgetattr(STACK[-1], co_names[namei>>1])
.If the low bit of
namei
is set, this will attempt to load a method namedco_names[namei>>1]
from theSTACK[-1]
object.STACK[-1]
is popped. This bytecode distinguishes two cases: ifSTACK[-1]
has a method with the correct name, the bytecode pushes the unbound method andSTACK[-1]
.STACK[-1]
will be used as the first argument (self
) byCALL
orCALL_KW
when calling the unbound method. Otherwise,NULL
and the object returned by the attribute lookup are pushed.Changed in version 3.12: If the low bit of
namei
is set, then aNULL
orself
is pushed to the stack before the attribute or unbound method respectively.
- LOAD_SUPER_ATTR(namei)¶
This opcode implements
super()
, both in its zero-argument and two-argument forms (e.g.super().method()
,super().attr
andsuper(cls, self).method()
,super(cls, self).attr
).It pops three values from the stack (from top of stack down):
self
: the first argument to the current methodcls
: the class within which the current method was definedthe global
super
With respect to its argument, it works similarly to
LOAD_ATTR
, except thatnamei
is shifted left by 2 bits instead of 1.The low bit of
namei
signals to attempt a method load, as withLOAD_ATTR
, which results in pushingNULL
and the loaded method. When it is unset a single value is pushed to the stack.The second-low bit of
namei
, if set, means that this was a two-argument call tosuper()
(unset means zero-argument).Added in version 3.12.
- COMPARE_OP(opname)¶
Performs a Boolean operation. The operation name can be found in
cmp_op[opname >> 5]
. If the fifth-lowest bit ofopname
is set (opname & 16
), the result should be coerced tobool
.Changed in version 3.13: The fifth-lowest bit of the oparg now indicates a forced conversion to
bool
.
- IS_OP(invert)¶
Performs
is
comparison, oris not
ifinvert
is 1.Added in version 3.9.
- CONTAINS_OP(invert)¶
Performs
in
comparison, ornot in
ifinvert
is 1.Added in version 3.9.
- IMPORT_NAME(namei)¶
Imports the module
co_names[namei]
.STACK[-1]
andSTACK[-2]
are popped and provide the fromlist and level arguments of__import__()
. The module object is pushed onto the stack. The current namespace is not affected: for a proper import statement, a subsequentSTORE_FAST
instruction modifies the namespace.
- IMPORT_FROM(namei)¶
Loads the attribute
co_names[namei]
from the module found inSTACK[-1]
. The resulting object is pushed onto the stack, to be subsequently stored by aSTORE_FAST
instruction.
- JUMP_FORWARD(delta)¶
Increments bytecode counter by delta.
- JUMP_BACKWARD(delta)¶
Decrements bytecode counter by delta. Checks for interrupts.
Added in version 3.11.
- JUMP_BACKWARD_NO_INTERRUPT(delta)¶
Decrements bytecode counter by delta. Does not check for interrupts.
Added in version 3.11.
- POP_JUMP_IF_TRUE(delta)¶
If
STACK[-1]
is true, increments the bytecode counter by delta.STACK[-1]
is popped.Changed in version 3.11: The oparg is now a relative delta rather than an absolute target. This opcode is a pseudo-instruction, replaced in final bytecode by the directed versions (forward/backward).
Changed in version 3.12: This is no longer a pseudo-instruction.
Changed in version 3.13: This instruction now requires an exact
bool
operand.
- POP_JUMP_IF_FALSE(delta)¶
If
STACK[-1]
is false, increments the bytecode counter by delta.STACK[-1]
is popped.Changed in version 3.11: The oparg is now a relative delta rather than an absolute target. This opcode is a pseudo-instruction, replaced in final bytecode by the directed versions (forward/backward).
Changed in version 3.12: This is no longer a pseudo-instruction.
Changed in version 3.13: This instruction now requires an exact
bool
operand.
- POP_JUMP_IF_NOT_NONE(delta)¶
If
STACK[-1]
is notNone
, increments the bytecode counter by delta.STACK[-1]
is popped.Added in version 3.11.
Changed in version 3.12: This is no longer a pseudo-instruction.
- POP_JUMP_IF_NONE(delta)¶
If
STACK[-1]
isNone
, increments the bytecode counter by delta.STACK[-1]
is popped.Added in version 3.11.
Changed in version 3.12: This is no longer a pseudo-instruction.
- FOR_ITER(delta)¶
STACK[-1]
is an iterator. Call its__next__()
method. If this yields a new value, push it on the stack (leaving the iterator below it). If the iterator indicates it is exhausted then the byte code counter is incremented by delta.Changed in version 3.12: Up until 3.11 the iterator was popped when it was exhausted.
- LOAD_GLOBAL(namei)¶
Loads the global named
co_names[namei>>1]
onto the stack.Changed in version 3.11: If the low bit of
namei
is set, then aNULL
is pushed to the stack before the global variable.
- LOAD_FAST(var_num)¶
Pushes a reference to the local
co_varnames[var_num]
onto the stack.Changed in version 3.12: This opcode is now only used in situations where the local variable is guaranteed to be initialized. It cannot raise
UnboundLocalError
.
- LOAD_FAST_BORROW(var_num)¶
Pushes a borrowed reference to the local
co_varnames[var_num]
onto the stack.Added in version 3.14.
- LOAD_FAST_LOAD_FAST(var_nums)¶
Pushes references to
co_varnames[var_nums >> 4]
andco_varnames[var_nums & 15]
onto the stack.Added in version 3.13.
- LOAD_FAST_BORROW_LOAD_FAST_BORROW(var_nums)¶
Pushes borrowed references to
co_varnames[var_nums >> 4]
andco_varnames[var_nums & 15]
onto the stack.Added in version 3.14.
- LOAD_FAST_CHECK(var_num)¶
Pushes a reference to the local
co_varnames[var_num]
onto the stack, raising anUnboundLocalError
if the local variable has not been initialized.Added in version 3.12.
- LOAD_FAST_AND_CLEAR(var_num)¶
Pushes a reference to the local
co_varnames[var_num]
onto the stack (or pushesNULL
onto the stack if the local variable has not been initialized) and setsco_varnames[var_num]
toNULL
.Added in version 3.12.
- STORE_FAST(var_num)¶
Stores
STACK.pop()
into the localco_varnames[var_num]
.
- STORE_FAST_STORE_FAST(var_nums)¶
Stores
STACK[-1]
intoco_varnames[var_nums >> 4]
andSTACK[-2]
intoco_varnames[var_nums & 15]
.Added in version 3.13.
- STORE_FAST_LOAD_FAST(var_nums)¶
Stores
STACK.pop()
into the localco_varnames[var_nums >> 4]
and pushes a reference to the localco_varnames[var_nums & 15]
onto the stack.Added in version 3.13.
- DELETE_FAST(var_num)¶
Deletes local
co_varnames[var_num]
.
- MAKE_CELL(i)¶
Creates a new cell in slot
i
. If that slot is nonempty then that value is stored into the new cell.Added in version 3.11.
- LOAD_DEREF(i)¶
Loads the cell contained in slot
i
of the “fast locals” storage. Pushes a reference to the object the cell contains on the stack.Changed in version 3.11:
i
is no longer offset by the length ofco_varnames
.
- LOAD_FROM_DICT_OR_DEREF(i)¶
Pops a mapping off the stack and looks up the name associated with slot
i
of the “fast locals” storage in this mapping. If the name is not found there, loads it from the cell contained in sloti
, similar toLOAD_DEREF
. This is used for loading closure variables in class bodies (which previously usedLOAD_CLASSDEREF
) and in annotation scopes within class bodies.Added in version 3.12.
- STORE_DEREF(i)¶
Stores
STACK.pop()
into the cell contained in sloti
of the “fast locals” storage.Changed in version 3.11:
i
is no longer offset by the length ofco_varnames
.
- DELETE_DEREF(i)¶
Empties the cell contained in slot
i
of the “fast locals” storage. Used by thedel
statement.Added in version 3.2.
Changed in version 3.11:
i
is no longer offset by the length ofco_varnames
.
- COPY_FREE_VARS(n)¶
Copies the
n
free (closure) variables from the closure into the frame. Removes the need for special code on the caller’s side when calling closures.Added in version 3.11.
- RAISE_VARARGS(argc)¶
Raises an exception using one of the 3 forms of the
raise
statement, depending on the value of argc:0:
raise
(re-raise previous exception)1:
raise STACK[-1]
(raise exception instance or type atSTACK[-1]
)2:
raise STACK[-2] from STACK[-1]
(raise exception instance or type atSTACK[-2]
with__cause__
set toSTACK[-1]
)
- CALL(argc)¶
Calls a callable object with the number of arguments specified by
argc
. On the stack are (in ascending order):The callable
self
orNULL
The remaining positional arguments
argc
is the total of the positional arguments, excludingself
.CALL
pops all arguments and the callable object off the stack, calls the callable object with those arguments, and pushes the return value returned by the callable object.Added in version 3.11.
Changed in version 3.13: The callable now always appears at the same position on the stack.
Changed in version 3.13: Calls with keyword arguments are now handled by
CALL_KW
.
- CALL_KW(argc)¶
Calls a callable object with the number of arguments specified by
argc
, including one or more named arguments. On the stack are (in ascending order):The callable
self
orNULL
The remaining positional arguments
The named arguments
A
tuple
of keyword argument names
argc
is the total of the positional and named arguments, excludingself
. The length of the tuple of keyword argument names is the number of named arguments.CALL_KW
pops all arguments, the keyword names, and the callable object off the stack, calls the callable object with those arguments, and pushes the return value returned by the callable object.Added in version 3.13.
- CALL_FUNCTION_EX(flags)¶
Calls a callable object with variable set of positional and keyword arguments. If the lowest bit of flags is set, the top of the stack contains a mapping object containing additional keyword arguments. Before the callable is called, the mapping object and iterable object are each “unpacked” and their contents passed in as keyword and positional arguments respectively.
CALL_FUNCTION_EX
pops all arguments and the callable object off the stack, calls the callable object with those arguments, and pushes the return value returned by the callable object.Added in version 3.6.
- PUSH_NULL¶
Pushes a
NULL
to the stack. Used in the call sequence to match theNULL
pushed byLOAD_METHOD
for non-method calls.Added in version 3.11.
- MAKE_FUNCTION¶
Pushes a new function object on the stack built from the code object at
STACK[-1]
.Changed in version 3.10: Flag value
0x04
is a tuple of strings instead of dictionaryChanged in version 3.11: Qualified name at
STACK[-1]
was removed.Changed in version 3.13: Extra function attributes on the stack, signaled by oparg flags, were removed. They now use
SET_FUNCTION_ATTRIBUTE
.
- SET_FUNCTION_ATTRIBUTE(flag)¶
Sets an attribute on a function object. Expects the function at
STACK[-1]
and the attribute value to set atSTACK[-2]
; consumes both and leaves the function atSTACK[-1]
. The flag determines which attribute to set:0x01
a tuple of default values for positional-only and positional-or-keyword parameters in positional order0x02
a dictionary of keyword-only parameters’ default values0x04
a tuple of strings containing parameters’ annotations0x08
a tuple containing cells for free variables, making a closure0x10
the annotate function for the function object
Added in version 3.13.
Changed in version 3.14: Added
0x10
to indicate the annotate function for the function object.
- BUILD_SLICE(argc)¶
Pushes a slice object on the stack. argc must be 2 or 3. If it is 2, implements:
end = STACK.pop() start = STACK.pop() STACK.append(slice(start, end))
if it is 3, implements:
step = STACK.pop() end = STACK.pop() start = STACK.pop() STACK.append(slice(start, end, step))
See the
slice()
built-in function for more information.
- EXTENDED_ARG(ext)¶
Prefixes any opcode which has an argument too big to fit into the default one byte. ext holds an additional byte which act as higher bits in the argument. For each opcode, at most three prefixal
EXTENDED_ARG
are allowed, forming an argument from two-byte to four-byte.
- CONVERT_VALUE(oparg)¶
Convert value to a string, depending on
oparg
:value = STACK.pop() result = func(value) STACK.append(result)
Used for implementing formatted string literals (f-strings).
Added in version 3.13.
- FORMAT_SIMPLE¶
Formats the value on top of stack:
value = STACK.pop() result = value.__format__("") STACK.append(result)
Used for implementing formatted string literals (f-strings).
Added in version 3.13.
- FORMAT_WITH_SPEC¶
Formats the given value with the given format spec:
spec = STACK.pop() value = STACK.pop() result = value.__format__(spec) STACK.append(result)
Used for implementing formatted string literals (f-strings).
Added in version 3.13.
- MATCH_CLASS(count)¶
STACK[-1]
is a tuple of keyword attribute names,STACK[-2]
is the class being matched against, andSTACK[-3]
is the match subject. count is the number of positional sub-patterns.Pop
STACK[-1]
,STACK[-2]
, andSTACK[-3]
. IfSTACK[-3]
is an instance ofSTACK[-2]
and has the positional and keyword attributes required by count andSTACK[-1]
, push a tuple of extracted attributes. Otherwise, pushNone
.Added in version 3.10.
Changed in version 3.11: Previously, this instruction also pushed a boolean value indicating success (
True
) or failure (False
).
- RESUME(context)¶
A no-op. Performs internal tracing, debugging and optimization checks.
The
context
operand consists of two parts. The lowest two bits indicate where theRESUME
occurs:0
The start of a function, which is neither a generator, coroutine nor an async generator1
After ayield
expression2
After ayield from
expression3
After anawait
expression
The next bit is
1
if the RESUME is at except-depth1
, and0
otherwise.Added in version 3.11.
Changed in version 3.13: The oparg value changed to include information about except-depth
- RETURN_GENERATOR¶
Create a generator, coroutine, or async generator from the current frame. Used as first opcode of in code object for the above mentioned callables. Clear the current frame and return the newly created generator.
Added in version 3.11.
- SEND(delta)¶
Equivalent to
STACK[-1] = STACK[-2].send(STACK[-1])
. Used inyield from
andawait
statements.If the call raises
StopIteration
, pop the top value from the stack, push the exception’svalue
attribute, and increment the bytecode counter by delta.Added in version 3.11.
- HAVE_ARGUMENT¶
This is not really an opcode. It identifies the dividing line between opcodes in the range [0,255] which don’t use their argument and those that do (
< HAVE_ARGUMENT
and>= HAVE_ARGUMENT
, respectively).If your application uses pseudo instructions or specialized instructions, use the
hasarg
collection instead.Changed in version 3.6: Now every instruction has an argument, but opcodes
< HAVE_ARGUMENT
ignore it. Before, only opcodes>= HAVE_ARGUMENT
had an argument.Changed in version 3.12: Pseudo instructions were added to the
dis
module, and for them it is not true that comparison withHAVE_ARGUMENT
indicates whether they use their arg.Deprecated since version 3.13: Use
hasarg
instead.
- CALL_INTRINSIC_1¶
Calls an intrinsic function with one argument. Passes
STACK[-1]
as the argument and setsSTACK[-1]
to the result. Used to implement functionality that is not performance critical.The operand determines which intrinsic function is called:
Operand
Description
INTRINSIC_1_INVALID
Not valid
INTRINSIC_PRINT
Prints the argument to standard out. Used in the REPL.
INTRINSIC_IMPORT_STAR
Performs
import *
for the named module.INTRINSIC_STOPITERATION_ERROR
Extracts the return value from a
StopIteration
exception.INTRINSIC_ASYNC_GEN_WRAP
Wraps an async generator value
INTRINSIC_UNARY_POSITIVE
Performs the unary
+
operationINTRINSIC_LIST_TO_TUPLE
Converts a list to a tuple
INTRINSIC_TYPEVAR
Creates a
typing.TypeVar
INTRINSIC_PARAMSPEC
Creates a
typing.ParamSpec
INTRINSIC_TYPEVARTUPLE
Creates a
typing.TypeVarTuple
INTRINSIC_SUBSCRIPT_GENERIC
Returns
typing.Generic
subscripted with the argumentINTRINSIC_TYPEALIAS
Creates a
typing.TypeAliasType
; used in thetype
statement. The argument is a tuple of the type alias’s name, type parameters, and value.Added in version 3.12.
- CALL_INTRINSIC_2¶
Calls an intrinsic function with two arguments. Used to implement functionality that is not performance critical:
arg2 = STACK.pop() arg1 = STACK.pop() result = intrinsic2(arg1, arg2) STACK.append(result)
The operand determines which intrinsic function is called:
Operand
Description
INTRINSIC_2_INVALID
Not valid
INTRINSIC_PREP_RERAISE_STAR
Calculates the
ExceptionGroup
to raise from atry-except*
.INTRINSIC_TYPEVAR_WITH_BOUND
Creates a
typing.TypeVar
with a bound.INTRINSIC_TYPEVAR_WITH_CONSTRAINTS
Creates a
typing.TypeVar
with constraints.INTRINSIC_SET_FUNCTION_TYPE_PARAMS
Sets the
__type_params__
attribute of a function.Added in version 3.12.
- LOAD_SPECIAL¶
Performs special method lookup on
STACK[-1]
. Iftype(STACK[-1]).__xxx__
is a method, leavetype(STACK[-1]).__xxx__; STACK[-1]
on the stack. Iftype(STACK[-1]).__xxx__
is not a method, leaveSTACK[-1].__xxx__; NULL
on the stack.Added in version 3.14.
Pseudo-instructions
These opcodes do not appear in Python bytecode. They are used by the compiler but are replaced by real opcodes or removed before bytecode is generated.
- SETUP_FINALLY(target)¶
Set up an exception handler for the following code block. If an exception occurs, the value stack level is restored to its current state and control is transferred to the exception handler at
target
.
- SETUP_CLEANUP(target)¶
Like
SETUP_FINALLY
, but in case of an exception also pushes the last instruction (lasti
) to the stack so thatRERAISE
can restore it. If an exception occurs, the value stack level and the last instruction on the frame are restored to their current state, and control is transferred to the exception handler attarget
.
- SETUP_WITH(target)¶
Like
SETUP_CLEANUP
, but in case of an exception one more item is popped from the stack before control is transferred to the exception handler attarget
.This variant is used in
with
andasync with
constructs, which push the return value of the context manager’s__enter__()
or__aenter__()
to the stack.
- POP_BLOCK¶
Marks the end of the code block associated with the last
SETUP_FINALLY
,SETUP_CLEANUP
orSETUP_WITH
.
- LOAD_CONST_IMMORTAL(consti)¶
Works as
LOAD_CONST
, but is more efficient for immortal objects.
- JUMP¶
- JUMP_NO_INTERRUPT¶
Undirected relative jump instructions which are replaced by their directed (forward/backward) counterparts by the assembler.
- JUMP_IF_TRUE¶
- JUMP_IF_FALSE¶
Conditional jumps which do not impact the stack. Replaced by the sequence
COPY 1
,TO_BOOL
,POP_JUMP_IF_TRUE/FALSE
.
- LOAD_CLOSURE(i)¶
Pushes a reference to the cell contained in slot
i
of the “fast locals” storage.Note that
LOAD_CLOSURE
is replaced withLOAD_FAST
in the assembler.Changed in version 3.13: This opcode is now a pseudo-instruction.
Opcode collections¶
These collections are provided for automatic introspection of bytecode instructions:
Changed in version 3.12: The collections now contain pseudo instructions and instrumented
instructions as well. These are opcodes with values >= MIN_PSEUDO_OPCODE
and >= MIN_INSTRUMENTED_OPCODE
.
- dis.opname¶
Sequence of operation names, indexable using the bytecode.
- dis.opmap¶
Dictionary mapping operation names to bytecodes.
- dis.cmp_op¶
Sequence of all compare operation names.
- dis.hasarg¶
Sequence of bytecodes that use their argument.
Added in version 3.12.
- dis.hasconst¶
Sequence of bytecodes that access a constant.
- dis.hasfree¶
Sequence of bytecodes that access a free (closure) variable. ‘free’ in this context refers to names in the current scope that are referenced by inner scopes or names in outer scopes that are referenced from this scope. It does not include references to global or builtin scopes.
- dis.hasname¶
Sequence of bytecodes that access an attribute by name.
- dis.hasjump¶
Sequence of bytecodes that have a jump target. All jumps are relative.
Added in version 3.13.
- dis.haslocal¶
Sequence of bytecodes that access a local variable.
- dis.hascompare¶
Sequence of bytecodes of Boolean operations.
- dis.hasexc¶
Sequence of bytecodes that set an exception handler.
Added in version 3.12.
- dis.hasjrel¶
Sequence of bytecodes that have a relative jump target.
Deprecated since version 3.13: All jumps are now relative. Use
hasjump
.
- dis.hasjabs¶
Sequence of bytecodes that have an absolute jump target.
Deprecated since version 3.13: All jumps are now relative. This list is empty.