dis
Source code: Lib/dis.py
import dis def myfunc(alist): return len(alist)
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.
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.
3.6 Use 2 bytes for each instruction. Previously the number of bytes varied by instruction.
3.10 The argument of jump, exception handling and loop instructions is now the instruction offset rather than the byte offset.
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
.
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 0 RESUME 0
- <BLANKLINE>
- 3 2 LOAD_GLOBAL 1 (NULL + len)
12 LOAD_FAST 0 (alist) 14 CALL 1 22 RETURN_VALUE
(The "2" is a line number).
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.
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 a Bytecode
instance yields the bytecode operations as Instruction
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 means .dis
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.
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
.
3.7 This can now handle coroutine and asynchronous generator objects.
3.11 Added the show_caches and adaptive parameters.
Example:
>>> bytecode = dis.Bytecode(myfunc) >>> for instr in bytecode: ... print(instr.opname) ... RESUME LOAD_GLOBAL LOAD_FAST CALL RETURN_VALUE
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:
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.
3.2
3.7 This can now handle coroutine and asynchronous generator objects.
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.
3.2
3.4 Added file parameter.
dis(x=None, *, file=None, depth=None, show_caches=False, adaptive=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 (the code of comprehensions, generator expressions and nested functions, and the code used for building nested classes). 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.
3.4 Added file parameter.
3.7 Implemented recursive disassembling and added depth parameter.
3.7 This can now handle coroutine and asynchronous generator objects.
3.11 Added the show_caches and adaptive parameters.
distb(tb=None, *, file=None, show_caches=False, adaptive=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.
3.4 Added file parameter.
3.11 Added the show_caches and adaptive parameters.
disassemble(code, lasti=-1, , file=None, show_caches=False, adaptive=False) disco(code, lasti=-1,, file=None, show_caches=False, adaptive=False)
Disassemble a code object, indicating the last instruction if lasti was provided. The output is divided in the following columns:
- the line number, for the first instruction of each line
- 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.
3.4 Added file parameter.
3.11 Added the show_caches and adaptive parameters.
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 show_caches and adaptive parameters work as they do in dis
.
3.4
3.11 Added the show_caches and adaptive parameters.
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.
3.6 Line numbers can be decreasing. Before, they were always increasing.
3.10 The 626
co_lines
method is used instead of the co_firstlineno
and co_lnotab
attributes of the code object.
findlabels(code)
Detect all offsets in the raw compiled bytecode string code which are jump targets, and return a list of these offsets.
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 is False
, it will return the stack effect of not jumping. And if jump is None
(default), it will return the maximal stack effect of both cases.
3.4
3.8 Added jump parameter.
The get_instructions
function and Bytecode
class provide details of bytecode instructions as Instruction
instances:
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
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
starts_line
line started by this opcode (if any), otherwise None
is_jump_target
True
if other code jumps to here, otherwise False
positions
dis.Positions
object holding the start and end locations that are covered by this instruction.
3.4
3.11
Field positions
is added.
In case the information is not available, some fields might be None
.
lineno
end_lineno
col_offset
end_col_offset
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.
POP_TOP
Removes the top-of-stack item.:
STACK.pop()
END_FOR
Removes the top two values from the stack. Equivalent to POP_TOP; POP_TOP. Used to clean up at the end of loops, hence the name.
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])
3.11
SWAP (i)
Swap the top of the stack with the i-th element.:
STACK[-i], STACK[-1] = stack[-1], STACK[-i]
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 with show_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.
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]
.
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, implements STACK[-1] = iter(STACK[-1])
.
3.5
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)
3.11
BINARY_SUBSCR
Implements:
key = STACK.pop()
container = STACK.pop()
STACK.append(container[index])
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])
3.12
STORE_SLICE
Implements:
end = STACK.pop()
start = STACK.pop()
container = STACK.pop()
values = STACK.pop()
container[start:end] = value
3.12
Coroutine opcodes
GET_AWAITABLE (where)
Implements STACK[-1] = get_awaitable(STACK[-1])
, where get_awaitable(o)
returns o
if o
is a coroutine object or a generator object with the CO_ITERABLE_COROUTINE flag, or resolves o.__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__
3.5
3.11 Previously, this instruction did not have an oparg.
GET_AITER
Implements STACK[-1] = STACK[-1].__aiter__()
.
3.5
3.7 Returning awaitable objects from __aiter__
is no longer supported.
GET_ANEXT
Implement STACK.append(get_awaitable(STACK[-1].__anext__()))
to the stack. See GET_AWAITABLE
for details about get_awaitable
.
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 in STACK[-2]
and the raised exception in STACK[-1]
. Both are popped. If the exception is not StopAsyncIteration
, it is re-raised.
3.8
3.11 Exception representation on the stack now consist of one, not three, items.
CLEANUP_THROW
Handles an exception raised during a ~generator.throw
or ~generator.close
call through the current frame. If STACK[-1]
is an instance of StopIteration
, pop three values from the stack and push its value
member. Otherwise, re-raise STACK[-1]
.
3.12
BEFORE_ASYNC_WITH
Resolves __aenter__
and __aexit__
from STACK[-1]
. Pushes __aexit__
and result of __aenter__()
to the stack:
STACK.extend((__aexit__, __aenter__())
3.5
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.
3.1
3.8 Map value is STACK[-1]
and map key is STACK[-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.
RETURN_CONST (consti)
Returns with co_consts[consti]
to the caller of the function.
3.12
YIELD_VALUE
Yields STACK.pop()
from a generator
.
3.11 oparg set to be the stack depth.
3.12 oparg set to be the exception block depth, for efficient closing of generators.
SETUP_ANNOTATIONS
Checks whether __annotations__
is defined in locals()
, if not it is set up to an empty dict
. This opcode is only emitted if a class or module body contains variable annotations <variable annotation>
statically.
3.6
POP_EXCEPT
Pops a value from the stack, which is used to restore the exception state.
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.
3.9
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.
3.11
CHECK_EXC_MATCH
Performs exception matching for except
. Tests whether the STACK[-2]
is an exception matching STACK[-1]
. Pops STACK[-1] and pushes the boolean result of the test.
3.11
CHECK_EG_MATCH
Performs exception matching for except*
. Applies split(STACK[-1])
on the exception group representing STACK[-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 pushes None
.
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 a with
statement.
3.9
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_ASSERTION_ERROR
Pushes AssertionError
onto the stack. Used by the assert
statement.
3.9
LOAD_BUILD_CLASS
Pushes builtins.__build_class__
onto the stack. It is later called to construct a class.
BEFORE_WITH
This opcode performs several operations before a with block starts. First, it loads ~object.__exit__
from the context manager and pushes it onto the stack for later use by WITH_EXCEPT_START
. Then, ~object.__enter__
is called. Finally, the result of calling the __enter__()
method is pushed onto the stack.
3.11
GET_LEN
Perform STACK.append(len(STACK[-1]))
.
3.10
MATCH_MAPPING
If STACK[-1]
is an instance of collections.abc.Mapping
(or, more technically: if it has the Py_TPFLAGS_MAPPING
flag set in its :c~PyTypeObject.tp_flags
), push True
onto the stack. Otherwise, push False
.
3.10
MATCH_SEQUENCE
If STACK[-1]
is an instance of collections.abc.Sequence
and is not an instance of str
/bytes
/bytearray
(or, more technically: if it has the Py_TPFLAGS_SEQUENCE
flag set in its :c~PyTypeObject.tp_flags
), push True
onto the stack. Otherwise, push False
.
3.10
MATCH_KEYS
STACK[-1]
is a tuple of mapping keys, and STACK[-2]
is the match subject. If STACK[-2]
contains all of the keys in STACK[-1]
, push a tuple
containing the corresponding values. Otherwise, push None
.
3.10
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 attribute co_names
of the code object. The compiler tries to use STORE_FAST
or STORE_GLOBAL
if possible.
DELETE_NAME (namei)
Implements del name
, where namei is the index into co_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.:
STACK.extend(STACK.pop()[:count:-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 as STACK.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
.
DELETE_ATTR (namei)
Implements:
obj = STACK.pop()
del obj.name
where namei is the index of name into co_names
.
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_NAME (namei)
Pushes the value associated with co_names[namei]
onto the stack.
BUILD_TUPLE (count)
Creates a tuple consuming count items from the stack, and pushes the resulting tuple onto the stack.:
assert count > 0
STACK, values = STACK[:-count], STACK[-count:]
STACK.append(tuple(values))
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]}
.
3.5 The dictionary is created from stack items instead of creating an empty dictionary pre-sized to hold count items.
BUILD_CONST_KEY_MAP (count)
The version of BUILD_MAP
specialized for constant keys. Pops the top element on the stack which contains a tuple of keys, then starting from STACK[-2]
, pops count values to form values in the built dictionary.
3.6
BUILD_STRING (count)
Concatenates count strings from the stack and pushes the resulting string onto the stack.
3.6
LIST_EXTEND (i)
Implements:
seq = STACK.pop()
list.extend(STACK[-i], seq)
Used to build lists.
3.9
SET_UPDATE (i)
Implements:
seq = STACK.pop()
set.update(STACK[-i], seq)
Used to build sets.
3.9
DICT_UPDATE (i)
Implements:
map = STACK.pop()
dict.update(STACK[-i], map)
Used to build dicts.
3.9
DICT_MERGE (i)
Like DICT_UPDATE
but raises an exception for duplicate keys.
3.9
LOAD_ATTR (namei)
If the low bit of namei
is not set, this replaces STACK[-1]
with getattr(STACK[-1], co_names[namei>>1])
.
If the low bit of namei
is set, this will attempt to load a method named co_names[namei>>1]
from the STACK[-1]
object. STACK[-1]
is popped. This bytecode distinguishes two cases: if STACK[-1]
has a method with the correct name, the bytecode pushes the unbound method and STACK[-1]
. STACK[-1]
will be used as the first argument (self
) by CALL
when calling the unbound method. Otherwise, NULL
and the object return by the attribute lookup are pushed.
3.12 If the low bit of namei
is set, then a NULL
or self
is pushed to the stack before the attribute or unbound method respectively.
COMPARE_OP (opname)
Performs a Boolean operation. The operation name can be found in cmp_op[opname]
.
IS_OP (invert)
Performs is
comparison, or is not
if invert
is 1.
3.9
CONTAINS_OP (invert)
Performs in
comparison, or not in
if invert
is 1.
3.9
IMPORT_NAME (namei)
Imports the module co_names[namei]
. STACK[-1]
and STACK[-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 subsequent STORE_FAST
instruction modifies the namespace.
IMPORT_FROM (namei)
Loads the attribute co_names[namei]
from the module found in STACK[-1]
. The resulting object is pushed onto the stack, to be subsequently stored by a STORE_FAST
instruction.
JUMP_FORWARD (delta)
Increments bytecode counter by delta.
JUMP_BACKWARD (delta)
Decrements bytecode counter by delta. Checks for interrupts.
3.11
JUMP_BACKWARD_NO_INTERRUPT (delta)
Decrements bytecode counter by delta. Does not check for interrupts.
3.11
POP_JUMP_IF_TRUE (delta)
If STACK[-1]
is true, increments the bytecode counter by delta. STACK[-1]
is popped.
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).
3.12 This is no longer a pseudo-instruction.
POP_JUMP_IF_FALSE (delta)
If STACK[-1]
is false, increments the bytecode counter by delta. STACK[-1]
is popped.
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).
3.12 This is no longer a pseudo-instruction.
POP_JUMP_IF_NOT_NONE (delta)
If STACK[-1]
is not None
, increments the bytecode counter by delta. STACK[-1]
is popped.
This opcode is a pseudo-instruction, replaced in final bytecode by the directed versions (forward/backward).
3.11
3.12 This is no longer a pseudo-instruction.
POP_JUMP_IF_NONE (delta)
If STACK[-1]
is None
, increments the bytecode counter by delta. STACK[-1]
is popped.
This opcode is a pseudo-instruction, replaced in final bytecode by the directed versions (forward/backward).
3.11
3.12 This is no longer a pseudo-instruction.
FOR_ITER (delta)
STACK[-1]
is an iterator
. Call its ~iterator.__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.
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.
3.11 If the low bit of namei
is set, then a NULL
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.
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_CHECK (var_num)
Pushes a reference to the local co_varnames[var_num]
onto the stack, raising an UnboundLocalError
if the local variable has not been initialized.
3.12
STORE_FAST (var_num)
Stores STACK.pop()
into the local co_varnames[var_num]
.
DELETE_FAST (var_num)
Deletes local co_varnames[var_num]
.
MAKE_CELL (i)
Creates a new cell in slot i
. If that slot is empty then that value is stored into the new cell.
3.11
LOAD_CLOSURE (i)
Pushes a reference to the cell contained in slot i
of the "fast locals" storage. The name of the variable is co_fastlocalnames[i]
.
Note that LOAD_CLOSURE
is effectively an alias for LOAD_FAST
. It exists to keep bytecode a little more readable.
3.11 i
is no longer offset by the length of co_varnames
.
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.
3.11 i
is no longer offset by the length of co_varnames
.
LOAD_CLASSDEREF (i)
Much like LOAD_DEREF
but first checks the locals dictionary before consulting the cell. This is used for loading free variables in class bodies.
3.4
3.11 i
is no longer offset by the length of co_varnames
.
STORE_DEREF (i)
Stores STACK.pop()
into the cell contained in slot i
of the "fast locals" storage.
3.11 i
is no longer offset by the length of co_varnames
.
DELETE_DEREF (i)
Empties the cell contained in slot i
of the "fast locals" storage. Used by the del
statement.
3.2
3.11 i
is no longer offset by the length of co_varnames
.
COPY_FREE_VARS (n)
Copies the n
free variables from the closure into the frame. Removes the need for special code on the caller's side when calling closures.
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
, including the named arguments specified by the preceding KW_NAMES
, if any. On the stack are (in ascending order), either:
- NULL
- The callable
- The positional arguments
- The named arguments
or:
- The callable
self
- The remaining positional arguments
- The named arguments
argc
is the total of the positional and named arguments, excluding self
when a NULL
is not present.
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.
3.11
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.
3.6
PUSH_NULL
Pushes a NULL
to the stack. Used in the call sequence to match the NULL
pushed by LOAD_METHOD
for non-method calls.
3.11
KW_NAMES (consti)
Prefixes CALL
. Stores a reference to co_consts[consti]
into an internal variable for use by CALL
. co_consts[consti]
must be a tuple of strings.
3.11
MAKE_FUNCTION (flags)
Pushes a new function object on the stack. From bottom to top, the consumed stack must consist of values if the argument carries a specified flag value
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 closure- the code associated with the function (at
STACK[-2]
) - the
qualified name
of the function (atSTACK[-1]
)
3.10 Flag value 0x04
is a tuple of strings instead of dictionary
BUILD_SLICE (argc)
builtin: slice
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, stop))
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.
FORMAT_VALUE (flags)
Used for implementing formatted literal strings (f-strings). Pops an optional fmt_spec from the stack, then a required value. flags is interpreted as follows:
(flags & 0x03) == 0x00
: value is formatted as-is.(flags & 0x03) == 0x01
: callstr
on value before formatting it.(flags & 0x03) == 0x02
: callrepr
on value before formatting it.(flags & 0x03) == 0x03
: callascii
on value before formatting it.(flags & 0x04) == 0x04
: pop fmt_spec from the stack and use it, else use an empty fmt_spec.
Formatting is performed using :cPyObject_Format
. The result is pushed on the stack.
3.6
MATCH_CLASS (count)
STACK[-1]
is a tuple of keyword attribute names, STACK[-2]
is the class being matched against, and STACK[-3]
is the match subject. count is the number of positional sub-patterns.
Pop STACK[-1]
, STACK[-2]
, and STACK[-3]
. If STACK[-3]
is an instance of STACK[-2]
and has the positional and keyword attributes required by count and STACK[-1]
, push a tuple of extracted attributes. Otherwise, push None
.
3.10
3.11 Previously, this instruction also pushed a boolean value indicating success (True
) or failure (False
).
RESUME (where)
A no-op. Performs internal tracing, debugging and optimization checks.
The where
operand marks where the RESUME
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
3.11
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.
3.11
SEND (delta)
Equivalent to STACK[-1] = STACK[-2].send(STACK[-1])
. Used in yield from
and await
statements.
If the call raises StopIteration
, pop both items, push the exception's value
attribute, and increment the bytecode counter by delta.
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, use the hasarg
collection instead.
3.6 Now every instruction has an argument, but opcodes < HAVE_ARGUMENT
ignore it. Before, only opcodes >= HAVE_ARGUMENT
had an argument.
3.12 Pseudo instructions were added to the dis
module, and for them it is not true that comparison with HAVE_ARGUMENT
indicates whether they use their arg.
CALL_INTRINSIC_1
Calls an intrinsic function with one argument. Passes STACK[-1]
as the argument and sets STACK[-1]
to the result. Used to implement functionality that is necessary but not performance critical.
The operand determines which intrinsic function is called:
0
Not valid1
Prints the argument to standard out. Used in the REPL.2
Performsimport *
for the named module.3
Extracts the return value from aStopIteration
exception.4
Wraps an aync generator value5
Performs the unary+
operation6
Converts a list to a tuple
3.12
CALL_INTRINSIC_2
Calls an intrinsic function with two arguments. Passes STACK[-2]
, STACK[-1]
as the arguments and sets STACK[-1]
to the result. Used to implement functionality that is necessary but not performance critical.
The operand determines which intrinsic function is called:
0
Not valid1
Calculates theExceptionGroup
to raise from atry-except*
.
3.12
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 exception also pushes the last instruction (lasti
) to the stack so that RERAISE
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 at target
.
SETUP_WITH (target)
Like SETUP_CLEANUP
, but in case of exception one more item is popped from the stack before control is transferred to the exception handler at target
.
This variant is used in with
and async with
constructs, which push the return value of the context manager's ~object.__enter__
or ~object.__aenter__
to the stack.
POP_BLOCK
Marks the end of the code block associated with the last SETUP_FINALLY
, SETUP_CLEANUP
or SETUP_WITH
.
JUMP
JUMP_NO_INTERRUPT
Undirected relative jump instructions which are replaced by their directed (forward/backward) counterparts by the assembler.
LOAD_METHOD
Optimized unbound method lookup. Emitted as a LOAD_ATTR
opcode with a flag set in the arg.
These collections are provided for automatic introspection of bytecode instructions:
3.12 The collections now contain pseudo instructions as well. These are opcodes with values
>= MIN_PSEUDO_OPCODE
.
opname
Sequence of operation names, indexable using the bytecode.
opmap
Dictionary mapping operation names to bytecodes.
cmp_op
Sequence of all compare operation names.
hasarg
Sequence of bytecodes that use their argument.
3.12
hasconst
Sequence of bytecodes that access a constant.
hasfree
Sequence of bytecodes that access a free variable (note that '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).
hasname
Sequence of bytecodes that access an attribute by name.
hasjrel
Sequence of bytecodes that have a relative jump target.
hasjabs
Sequence of bytecodes that have an absolute jump target.
haslocal
Sequence of bytecodes that access a local variable.
hascompare
Sequence of bytecodes of Boolean operations.
hasexc
Sequence of bytecodes that set an exception handler.
3.12