# `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`.

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

      3           2 LOAD_GLOBAL              1 (NULL + len)
                 14 LOAD_FAST                0 (alist)
                 16 PRECALL                  1
                 20 CALL                     1
                 30 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] [infile]

The following options are accepted:

-h, --help

  Display usage and exit.

-C, --show-caches

  Show inline caches.

If `infile` is specified, its disassembled code will be written to stdout. Otherwise, disassembly is performed on compiled source code recieved from stdin.

## Bytecode analysis

New 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)

  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.

  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.

Example:

    >>> bytecode = dis.Bytecode(myfunc)
    >>> for instr in bytecode:
    ...     print(instr.opname)
    ...
    RESUME
    LOAD_GLOBAL
    LOAD_FAST
    PRECALL
    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.

  New 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.

  New 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)

  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.

  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.

dis.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.

  Changed in version 3.4: Added file parameter.

  Changed in version 3.11: Added the show_caches and adaptive parameters.

dis.disassemble(code, lasti=- 1, *, file=None, show_caches=False, adaptive=False)
dis.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:

  1. the line number, for the first instruction of each line

  2. the current instruction, indicated as `-->`,

  3. a labelled instruction, indicated with `>>`,

  4. the address of the instruction,

  5. the operation code name,

  6. operation parameters, and

  7. 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.

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 show_caches and adaptive parameters work as they do in `dis()`.

  New in version 3.4.

  Changed in version 3.11: Added the show_caches and adaptive parameters.

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 the `co_firstlineno` and `co_lnotab` attributes of the code object.

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 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.

  New in version 3.4.

  Changed in version 3.8: Added jump parameter.

## 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

  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.

  New in version 3.4.

  Changed in version 3.11: Field `positions` is added.

class dis.Positions

  In case the information is not available, some fields might be `None`.

  lineno
  end_lineno
  col_offset
  end_col_offset

  New in version 3.11.

The Python compiler currently generates the following bytecode instructions.

General instructions

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 (TOS) item.

COPY(i)

  Push the i-th item to the top of the stack. The item is not removed from its original location.

  New in version 3.11.

SWAP(i)

  Swap TOS with the item at position i.

  New 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 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.

  New 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_POSITIVE

  Implements `TOS = +TOS`.

UNARY_NEGATIVE

  Implements `TOS = -TOS`.

UNARY_NOT

  Implements `TOS = not TOS`.

UNARY_INVERT

  Implements `TOS = ~TOS`.

GET_ITER

  Implements `TOS = iter(TOS)`.

GET_YIELD_FROM_ITER

  If `TOS` is a generator iterator or coroutine object it is left as is. Otherwise, implements `TOS = iter(TOS)`.

  New in version 3.5.

Binary and in-place operations

Binary operations remove the top of the stack (TOS) and the second top-most stack item (TOS1) from the stack. They perform the operation, and put the result back on the stack.

In-place operations are like binary operations, in that they remove TOS and TOS1, and push the result back on the stack, but the operation is done in-place when TOS1 supports it, and the resulting TOS may be (but does not have to be) the original TOS1.

BINARY_OP(op)

  Implements the binary and in-place operators (depending on the value of op).

  New in version 3.11.

BINARY_SUBSCR

  Implements `TOS = TOS1[TOS]`.

STORE_SUBSCR

  Implements `TOS1[TOS] = TOS2`.

DELETE_SUBSCR

  Implements `del TOS1[TOS]`.

Coroutine opcodes

GET_AWAITABLE(where)

  Implements `TOS = get_awaitable(TOS)`, 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__`

  New in version 3.5.

  Changed in version 3.11: Previously, this instruction did not have an oparg.

GET_AITER

  Implements `TOS = TOS.__aiter__()`.

  New in version 3.5.

  Changed in version 3.7: Returning awaitable objects from `__aiter__` is no longer supported.

GET_ANEXT

  Pushes `get_awaitable(TOS.__anext__())` to the stack. See `GET_AWAITABLE` for details about `get_awaitable`.

  New 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 in TOS1 and the raised exception in TOS. Both are popped. If the exception is not `StopAsyncIteration`, it is re-raised.

  New in version 3.8.

  Changed in version 3.11: Exception representation on the stack now consist of one, not three, items.

BEFORE_ASYNC_WITH

  Resolves `__aenter__` and `__aexit__` from the object on top of the stack. Pushes `__aexit__` and result of `__aenter__()` to the stack.

  New in version 3.5.

Miscellaneous opcodes

PRINT_EXPR

  Implements the expression statement for the interactive mode. TOS is removed from the stack and printed. In non-interactive mode, an expression statement is terminated with `POP_TOP`.

SET_ADD(i)

  Calls `set.add(TOS1[-i], TOS)`. Used to implement set comprehensions.

LIST_APPEND(i)

  Calls `list.append(TOS1[-i], TOS)`. Used to implement list comprehensions.

MAP_ADD(i)

  Calls `dict.__setitem__(TOS1[-i], TOS1, TOS)`. Used to implement dict comprehensions.

  New in version 3.1.

  Changed in version 3.8: Map value is TOS and map key is TOS1. 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 TOS to the caller of the function.

YIELD_VALUE

  Pops TOS and yields it from a generator.

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 statically.

  New in version 3.6.

IMPORT_STAR

  Loads all symbols not starting with `'_'` directly from the module TOS to the local namespace. The module is popped after loading all names. This opcode implements `from module import *`.

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.

  New 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.

  New in version 3.11.

CHECK_EXC_MATCH

  Performs exception matching for `except`. Tests whether the TOS1 is an exception matching TOS. Pops TOS and pushes the boolean result of the test.

  New in version 3.11.

CHECK_EG_MATCH

  Performs exception matching for `except*`. Applies `split(TOS)` on the exception group representing TOS1.

  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`.

  New in version 3.11.

PREP_RERAISE_STAR

  Combines the raised and reraised exceptions list from TOS, into an exception group to propagate from a try-except* block. Uses the original exception group from TOS1 to reconstruct the structure of reraised exceptions. Pops two items from the stack and pushes the exception to reraise or `None` if there isn’t one.

  New 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 a `with` statement.

  New 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_ASSERTION_ERROR

  Pushes `AssertionError` onto the stack. Used by the `assert` statement.

  New in version 3.9.

LOAD_BUILD_CLASS

  Pushes `builtins.__build_class__()` onto the stack. It is later called to construct a class.

BEFORE_WITH(delta)

  This opcode performs several operations before a with block starts. First, it loads `__exit__()` from the context manager and pushes it onto the stack for later use by `WITH_EXCEPT_START`. Then, `__enter__()` is called. Finally, the result of calling the `__enter__()` method is pushed onto the stack.

  New in version 3.11.

GET_LEN

  Push `len(TOS)` onto the stack.

  New in version 3.10.

MATCH_MAPPING

  If TOS is an instance of `collections.abc.Mapping` (or, more technically: if it has the `Py_TPFLAGS_MAPPING` flag set in its `tp_flags`), push `True` onto the stack. Otherwise, push `False`.

  New in version 3.10.

MATCH_SEQUENCE

  If TOS 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 `tp_flags`), push `True` onto the stack. Otherwise, push `False`.

  New in version 3.10.

MATCH_KEYS

  TOS is a tuple of mapping keys, and TOS1 is the match subject. If TOS1 contains all of the keys in TOS, push a `tuple` containing the corresponding values. Otherwise, push `None`.

  New 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 = TOS`. 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 TOS into count individual values, which are put onto the stack right-to-left.

UNPACK_EX(counts)

  Implements assignment with a starred target: Unpacks an iterable in TOS 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 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 resulting values are put onto the stack right-to-left.

STORE_ATTR(namei)

  Implements `TOS.name = TOS1`, where namei is the index of name in `co_names`.

DELETE_ATTR(namei)

  Implements `del TOS.name`, using namei as index 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.

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: `{..., TOS3: TOS2, TOS1: TOS}`.

  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_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 `TOS1`, pops count values to form values in the built dictionary.

  New in version 3.6.

BUILD_STRING(count)

  Concatenates count strings from the stack and pushes the resulting string onto the stack.

  New in version 3.6.

LIST_TO_TUPLE

  Pops a list from the stack and pushes a tuple containing the same values.

  New in version 3.9.

LIST_EXTEND(i)

  Calls `list.extend(TOS1[-i], TOS)`. Used to build lists.

  New in version 3.9.

SET_UPDATE(i)

  Calls `set.update(TOS1[-i], TOS)`. Used to build sets.

  New in version 3.9.

DICT_UPDATE(i)

  Calls `dict.update(TOS1[-i], TOS)`. Used to build dicts.

  New in version 3.9.

DICT_MERGE(i)

  Like `DICT_UPDATE` but raises an exception for duplicate keys.

  New in version 3.9.

LOAD_ATTR(namei)

  Replaces TOS with `getattr(TOS, co_names[namei])`.

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.

  New in version 3.9.

CONTAINS_OP(invert)

  Performs `in` comparison, or `not in` if `invert` is 1.

  New in version 3.9.

IMPORT_NAME(namei)

  Imports the module `co_names[namei]`. TOS and TOS1 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 TOS. 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.

  New in version 3.11.

JUMP_BACKWARD_NO_INTERRUPT(delta)

  Decrements bytecode counter by delta. Does not check for interrupts.

  New in version 3.11.

POP_JUMP_FORWARD_IF_TRUE(delta)

  If TOS is true, increments the bytecode counter by delta. TOS is popped.

  New in version 3.11.

POP_JUMP_BACKWARD_IF_TRUE(delta)

  If TOS is true, decrements the bytecode counter by delta. TOS is popped.

  New in version 3.11.

POP_JUMP_FORWARD_IF_FALSE(delta)

  If TOS is false, increments the bytecode counter by delta. TOS is popped.

  New in version 3.11.

POP_JUMP_BACKWARD_IF_FALSE(delta)

  If TOS is false, decrements the bytecode counter by delta. TOS is popped.

  New in version 3.11.

POP_JUMP_FORWARD_IF_NOT_NONE(delta)

  If TOS is not `None`, increments the bytecode counter by delta. TOS is popped.

  New in version 3.11.

POP_JUMP_BACKWARD_IF_NOT_NONE(delta)

  If TOS is not `None`, decrements the bytecode counter by delta. TOS is popped.

  New in version 3.11.

POP_JUMP_FORWARD_IF_NONE(delta)

  If TOS is `None`, increments the bytecode counter by delta. TOS is popped.

  New in version 3.11.

POP_JUMP_BACKWARD_IF_NONE(delta)

  If TOS is `None`, decrements the bytecode counter by delta. TOS is popped.

  New in version 3.11.

JUMP_IF_TRUE_OR_POP(delta)

  If TOS is true, increments the bytecode counter by delta and leaves TOS on the stack. Otherwise (TOS is false), TOS is popped.

  New in version 3.1.

  Changed in version 3.11: The oparg is now a relative delta rather than an absolute target.

JUMP_IF_FALSE_OR_POP(delta)

  If TOS is false, increments the bytecode counter by delta and leaves TOS on the stack. Otherwise (TOS is true), TOS is popped.

  New in version 3.1.

  Changed in version 3.11: The oparg is now a relative delta rather than an absolute target.

FOR_ITER(delta)

  TOS 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, TOS is popped, and the byte code counter is incremented by delta.

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 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.

STORE_FAST(var_num)

  Stores TOS 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 nonempty then that value is stored into the new cell.

  New in version 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.

  Changed in version 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.

  Changed in version 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.

  New in version 3.4.

  Changed in version 3.11: `i` is no longer offset by the length of `co_varnames`.

STORE_DEREF(i)

  Stores TOS into the cell contained in slot `i` of the “fast locals” storage.

  Changed in version 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.

  New in version 3.2.

  Changed in version 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.

  New 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 TOS` (raise exception instance or type at `TOS`)

  - 2: `raise TOS1 from TOS` (raise exception instance or type at `TOS1` with `__cause__` set to `TOS`)

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.

  New in version 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.

  New in version 3.6.

LOAD_METHOD(namei)

  Loads a method named `co_names[namei]` from the TOS object. TOS is popped. This bytecode distinguishes two cases: if TOS has a method with the correct name, the bytecode pushes the unbound method and TOS. TOS 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.

  New in version 3.7.

PRECALL(argc)

  Prefixes `CALL`. Logically this is a no op. It exists to enable effective specialization of calls. `argc` is the number of arguments as described in `CALL`.

  New in version 3.11.

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.

  New in version 3.11.

KW_NAMES(i)

  Prefixes `PRECALL`. Stores a reference to `co_consts[consti]` into an internal variable for use by `CALL`. `co_consts[consti]` must be a tuple of strings.

  New in version 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 order

  - `0x02` a dictionary of keyword-only parameters’ default values

  - `0x04` a tuple of strings containing parameters’ annotations

  - `0x08` a tuple containing cells for free variables, making a closure

  - the code associated with the function (at TOS)

  Changed in version 3.10: Flag value `0x04` is a tuple of strings instead of dictionary

  Changed in version 3.11: Qualified name at TOS was removed.

BUILD_SLICE(argc)

  Pushes a slice object on the stack. argc must be 2 or 3. If it is 2, `slice(TOS1, TOS)` is pushed; if it is 3, `slice(TOS2, TOS1, TOS)` is pushed. 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`: call `str()` on value before formatting it.

  - `(flags & 0x03) == 0x02`: call `repr()` on value before formatting it.

  - `(flags & 0x03) == 0x03`: call `ascii()` 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 `PyObject_Format()`. The result is pushed on the stack.

  New in version 3.6.

MATCH_CLASS(count)

  TOS is a tuple of keyword attribute names, TOS1 is the class being matched against, and TOS2 is the match subject. count is the number of positional sub-patterns.

  Pop TOS, TOS1, and TOS2. If TOS2 is an instance of TOS1 and has the positional and keyword attributes required by count and TOS, push a tuple of extracted attributes. Otherwise, push `None`.

  New in version 3.10.

  Changed in version 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

  > - `1` After a `yield` expression

  > - `2` After a `yield from` expression

  > - `3` After an `await` expression

  New in version 3.11.

RETURN_GENERATOR

  Create a generator, coroutine, or async generator from the current frame. Clear the current frame and return the newly created generator.

  New in version 3.11.

SEND

  Sends `None` to the sub-generator of this generator. Used in `yield from` and `await` statements.

  New in version 3.11.

ASYNC_GEN_WRAP

  Wraps the value on top of the stack in an `async_generator_wrapped_value`. Used to yield in async generators.

  New in version 3.11.

HAVE_ARGUMENT

  This is not really an opcode. It identifies the dividing line between opcodes which don’t use their argument and those that do (`< HAVE_ARGUMENT` and `>= HAVE_ARGUMENT`, respectively).

  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.

## Opcode collections

These collections are provided for automatic introspection of bytecode instructions:

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.hasconst

  Sequence of bytecodes that access a constant.

dis.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).

dis.hasname

  Sequence of bytecodes that access an attribute by name.

dis.hasjrel

  Sequence of bytecodes that have a relative jump target.

dis.hasjabs

  Sequence of bytecodes that have an absolute jump target.

dis.haslocal

  Sequence of bytecodes that access a local variable.

dis.hascompare

  Sequence of bytecodes of Boolean operations.