FM / library

/usr/share/doc/python3-docs/html/_sources/library/

/usr/share/doc/python3-docs/html/_sources/library

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Edit: /usr/share/doc/python3-docs/html/_sources/library/dis.rst.txt (32567B)

:mod:`dis` --- Disassembler for Python bytecode
===============================================

.. module:: dis
   :synopsis: Disassembler for Python bytecode.

**Source code:** :source:`Lib/dis.py`

--------------

The :mod:`dis` module supports the analysis of CPython :term:`bytecode` by
disassembling it. The CPython bytecode which this module takes as an input is
defined in the file :file:`Include/opcode.h` and used by the compiler and the
interpreter.

.. impl-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.

.. versionchanged:: 3.6
      Use 2 bytes for each instruction. Previously the number of bytes varied
      by instruction.

Example: Given the function :func:`myfunc`::

def myfunc(alist):
       return len(alist)

the following command can be used to display the disassembly of
:func:`myfunc`::

>>> dis.dis(myfunc)
     2           0 LOAD_GLOBAL              0 (len)
                 2 LOAD_FAST                0 (alist)
                 4 CALL_FUNCTION            1
                 6 RETURN_VALUE

(The "2" is a line number).

Bytecode analysis
-----------------

.. versionadded:: 3.4

The bytecode analysis API allows pieces of Python code to be wrapped in a
:class:`Bytecode` object that provides easy access to details of the compiled
code.

.. class:: Bytecode(x, *, first_line=None, current_offset=None)

Analyse the bytecode corresponding to a function, generator, method, string
   of source code, or a code object (as returned by :func:`compile`).

This is a convenience wrapper around many of the functions listed below, most
   notably :func:`get_instructions`, as iterating over a :class:`Bytecode`
   instance yields the bytecode operations as :class:`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 :meth:`.dis` will display a "current
   instruction" marker against the specified opcode.

.. classmethod:: from_traceback(tb)

Construct a :class:`Bytecode` instance from the given traceback, setting
      *current_offset* to the instruction responsible for the exception.

.. data:: codeobj

The compiled code object.

.. data:: first_line

The first source line of the code object (if available)

.. method:: dis()

Return a formatted view of the bytecode operations (the same as printed by
      :func:`dis.dis`, but returned as a multi-line string).

.. method:: info()

Return a formatted multi-line string with detailed information about the
      code object, like :func:`code_info`.

Example::

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

Analysis functions
------------------

The :mod:`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:

.. function:: code_info(x)

Return a formatted multi-line string with detailed code object information
   for the supplied function, generator, 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.

.. versionadded:: 3.2

.. function:: 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.

.. versionadded:: 3.2

.. versionchanged:: 3.4
      Added *file* parameter.

.. function:: dis(x=None, *, file=None)

Disassemble the *x* object.  *x* can denote either a module, a class, a
   method, a function, a generator, 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.  Strings are first compiled to code objects with the :func:`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.

.. versionchanged:: 3.4
      Added *file* parameter.

.. function:: distb(tb=None, *, file=None)

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.

.. versionchanged:: 3.4
      Added *file* parameter.

.. function:: disassemble(code, lasti=-1, *, file=None)
              disco(code, lasti=-1, *, file=None)

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.

.. versionchanged:: 3.4
      Added *file* parameter.

.. function:: get_instructions(x, *, first_line=None)

Return an iterator over the instructions in the supplied function, method,
   source code string or code object.

The iterator generates a series of :class:`Instruction` named tuples giving
   the details of each operation in the supplied code.

.. versionadded:: 3.4

.. function:: findlinestarts(code)

This generator function uses the ``co_firstlineno`` and ``co_lnotab``
   attributes 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.
   See :source:`Objects/lnotab_notes.txt` for the ``co_lnotab`` format and
   how to decode it.

.. versionchanged:: 3.6
      Line numbers can be decreasing. Before, they were always increasing.

.. function:: findlabels(code)

Detect all offsets in the code object *code* which are jump targets, and
   return a list of these offsets.

.. function:: stack_effect(opcode, [oparg])

Compute the stack effect of *opcode* with argument *oparg*.

.. versionadded:: 3.4

.. _bytecodes:

Python Bytecode Instructions
----------------------------

The :func:`get_instructions` function and :class:`Bytecode` class provide
details of bytecode instructions as :class:`Instruction` instances:

.. class:: Instruction

Details for a bytecode operation

.. data:: opcode

numeric code for operation, corresponding to the opcode values listed
      below and the bytecode values in the :ref:`opcode_collections`.

.. data:: opname

human readable name for operation

.. data:: arg

numeric argument to operation (if any), otherwise ``None``

.. data:: argval

resolved arg value (if known), otherwise same as arg

.. data:: argrepr

human readable description of operation argument

.. data:: offset

start index of operation within bytecode sequence

.. data:: starts_line

line started by this opcode (if any), otherwise ``None``

.. data:: is_jump_target

``True`` if other code jumps to here, otherwise ``False``

.. versionadded:: 3.4

The Python compiler currently generates the following bytecode instructions.

**General instructions**

.. opcode:: NOP

Do nothing code.  Used as a placeholder by the bytecode optimizer.

.. opcode:: POP_TOP

Removes the top-of-stack (TOS) item.

.. opcode:: ROT_TWO

Swaps the two top-most stack items.

.. opcode:: ROT_THREE

Lifts second and third stack item one position up, moves top down to position
   three.

.. opcode:: DUP_TOP

Duplicates the reference on top of the stack.

.. versionadded:: 3.2

.. opcode:: DUP_TOP_TWO

Duplicates the two references on top of the stack, leaving them in the
   same order.

.. versionadded:: 3.2

**Unary operations**

Unary operations take the top of the stack, apply the operation, and push the
result back on the stack.

.. opcode:: UNARY_POSITIVE

Implements ``TOS = +TOS``.

.. opcode:: UNARY_NEGATIVE

Implements ``TOS = -TOS``.

.. opcode:: UNARY_NOT

Implements ``TOS = not TOS``.

.. opcode:: UNARY_INVERT

Implements ``TOS = ~TOS``.

.. opcode:: GET_ITER

Implements ``TOS = iter(TOS)``.

.. opcode:: GET_YIELD_FROM_ITER

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

.. versionadded:: 3.5

**Binary 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.

.. opcode:: BINARY_POWER

Implements ``TOS = TOS1 ** TOS``.

.. opcode:: BINARY_MULTIPLY

Implements ``TOS = TOS1 * TOS``.

.. opcode:: BINARY_MATRIX_MULTIPLY

Implements ``TOS = TOS1 @ TOS``.

.. versionadded:: 3.5

.. opcode:: BINARY_FLOOR_DIVIDE

Implements ``TOS = TOS1 // TOS``.

.. opcode:: BINARY_TRUE_DIVIDE

Implements ``TOS = TOS1 / TOS``.

.. opcode:: BINARY_MODULO

Implements ``TOS = TOS1 % TOS``.

.. opcode:: BINARY_ADD

Implements ``TOS = TOS1 + TOS``.

.. opcode:: BINARY_SUBTRACT

Implements ``TOS = TOS1 - TOS``.

.. opcode:: BINARY_SUBSCR

Implements ``TOS = TOS1[TOS]``.

.. opcode:: BINARY_LSHIFT

Implements ``TOS = TOS1 << TOS``.

.. opcode:: BINARY_RSHIFT

Implements ``TOS = TOS1 >> TOS``.

.. opcode:: BINARY_AND

Implements ``TOS = TOS1 & TOS``.

.. opcode:: BINARY_XOR

Implements ``TOS = TOS1 ^ TOS``.

.. opcode:: BINARY_OR

Implements ``TOS = TOS1 | TOS``.

**In-place operations**

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.

.. opcode:: INPLACE_POWER

Implements in-place ``TOS = TOS1 ** TOS``.

.. opcode:: INPLACE_MULTIPLY

Implements in-place ``TOS = TOS1 * TOS``.

.. opcode:: INPLACE_MATRIX_MULTIPLY

Implements in-place ``TOS = TOS1 @ TOS``.

.. versionadded:: 3.5

.. opcode:: INPLACE_FLOOR_DIVIDE

Implements in-place ``TOS = TOS1 // TOS``.

.. opcode:: INPLACE_TRUE_DIVIDE

Implements in-place ``TOS = TOS1 / TOS``.

.. opcode:: INPLACE_MODULO

Implements in-place ``TOS = TOS1 % TOS``.

.. opcode:: INPLACE_ADD

Implements in-place ``TOS = TOS1 + TOS``.

.. opcode:: INPLACE_SUBTRACT

Implements in-place ``TOS = TOS1 - TOS``.

.. opcode:: INPLACE_LSHIFT

Implements in-place ``TOS = TOS1 << TOS``.

.. opcode:: INPLACE_RSHIFT

Implements in-place ``TOS = TOS1 >> TOS``.

.. opcode:: INPLACE_AND

Implements in-place ``TOS = TOS1 & TOS``.

.. opcode:: INPLACE_XOR

Implements in-place ``TOS = TOS1 ^ TOS``.

.. opcode:: INPLACE_OR

Implements in-place ``TOS = TOS1 | TOS``.

.. opcode:: STORE_SUBSCR

Implements ``TOS1[TOS] = TOS2``.

.. opcode:: DELETE_SUBSCR

Implements ``del TOS1[TOS]``.

**Coroutine opcodes**

.. opcode:: GET_AWAITABLE

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__``.

.. versionadded:: 3.5

.. opcode:: GET_AITER

Implements ``TOS = get_awaitable(TOS.__aiter__())``.  See ``GET_AWAITABLE``
   for details about ``get_awaitable``

.. versionadded:: 3.5

.. opcode:: GET_ANEXT

Implements ``PUSH(get_awaitable(TOS.__anext__()))``.  See ``GET_AWAITABLE``
   for details about ``get_awaitable``

.. versionadded:: 3.5

.. opcode:: BEFORE_ASYNC_WITH

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

.. versionadded:: 3.5

.. opcode:: SETUP_ASYNC_WITH

Creates a new frame object.

.. versionadded:: 3.5

**Miscellaneous opcodes**

.. opcode:: 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 :opcode:`POP_TOP`.

.. opcode:: BREAK_LOOP

Terminates a loop due to a :keyword:`break` statement.

.. opcode:: CONTINUE_LOOP (target)

Continues a loop due to a :keyword:`continue` statement.  *target* is the
   address to jump to (which should be a :opcode:`FOR_ITER` instruction).

.. opcode:: SET_ADD (i)

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

.. opcode:: LIST_APPEND (i)

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

.. opcode:: MAP_ADD (i)

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

.. versionadded:: 3.1

For all of the :opcode:`SET_ADD`, :opcode:`LIST_APPEND` and :opcode:`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.

.. opcode:: RETURN_VALUE

Returns with TOS to the caller of the function.

.. opcode:: YIELD_VALUE

Pops TOS and yields it from a :term:`generator`.

.. opcode:: YIELD_FROM

Pops TOS and delegates to it as a subiterator from a :term:`generator`.

.. versionadded:: 3.3

.. opcode:: 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 :term:`variable annotations <variable annotation>`
   statically.

.. versionadded:: 3.6

.. opcode:: 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 *``.

.. opcode:: POP_BLOCK

Removes one block from the block stack.  Per frame, there is a stack of
   blocks, denoting nested loops, try statements, and such.

.. opcode:: POP_EXCEPT

Removes one block from the block stack. The popped block must be an exception
   handler block, as implicitly created when entering an except handler.  In
   addition to popping extraneous values from the frame stack, the last three
   popped values are used to restore the exception state.

.. opcode:: END_FINALLY

Terminates a :keyword:`finally` clause.  The interpreter recalls whether the
   exception has to be re-raised, or whether the function returns, and continues
   with the outer-next block.

.. opcode:: LOAD_BUILD_CLASS

Pushes :func:`builtins.__build_class__` onto the stack.  It is later called
   by :opcode:`CALL_FUNCTION` to construct a class.

.. opcode:: SETUP_WITH (delta)

This opcode performs several operations before a with block starts.  First,
   it loads :meth:`~object.__exit__` from the context manager and pushes it onto
   the stack for later use by :opcode:`WITH_CLEANUP`.  Then,
   :meth:`~object.__enter__` is called, and a finally block pointing to *delta*
   is pushed.  Finally, the result of calling the enter method is pushed onto
   the stack.  The next opcode will either ignore it (:opcode:`POP_TOP`), or
   store it in (a) variable(s) (:opcode:`STORE_FAST`, :opcode:`STORE_NAME`, or
   :opcode:`UNPACK_SEQUENCE`).

.. versionadded:: 3.2

.. opcode:: WITH_CLEANUP_START

Cleans up the stack when a :keyword:`with` statement block exits.  TOS is the
   context manager's :meth:`__exit__` bound method. Below TOS are 1--3 values
   indicating how/why the finally clause was entered:

* SECOND = ``None``
   * (SECOND, THIRD) = (``WHY_{RETURN,CONTINUE}``), retval
   * SECOND = ``WHY_*``; no retval below it
   * (SECOND, THIRD, FOURTH) = exc_info()

In the last case, ``TOS(SECOND, THIRD, FOURTH)`` is called, otherwise
   ``TOS(None, None, None)``.  Pushes SECOND and result of the call
   to the stack.

.. opcode:: WITH_CLEANUP_FINISH

Pops exception type and result of 'exit' function call from the stack.

If the stack represents an exception, *and* the function call returns a
   'true' value, this information is "zapped" and replaced with a single
   ``WHY_SILENCED`` to prevent :opcode:`END_FINALLY` from re-raising the
   exception.  (But non-local gotos will still be resumed.)

.. XXX explain the WHY stuff!

All of the following opcodes use their arguments.

.. opcode:: STORE_NAME (namei)

Implements ``name = TOS``. *namei* is the index of *name* in the attribute
   :attr:`co_names` of the code object. The compiler tries to use
   :opcode:`STORE_FAST` or :opcode:`STORE_GLOBAL` if possible.

.. opcode:: DELETE_NAME (namei)

Implements ``del name``, where *namei* is the index into :attr:`co_names`
   attribute of the code object.

.. opcode:: UNPACK_SEQUENCE (count)

Unpacks TOS into *count* individual values, which are put onto the stack
   right-to-left.

.. opcode:: 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.

.. opcode:: STORE_ATTR (namei)

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

.. opcode:: DELETE_ATTR (namei)

Implements ``del TOS.name``, using *namei* as index into :attr:`co_names`.

.. opcode:: STORE_GLOBAL (namei)

Works as :opcode:`STORE_NAME`, but stores the name as a global.

.. opcode:: DELETE_GLOBAL (namei)

Works as :opcode:`DELETE_NAME`, but deletes a global name.

.. opcode:: LOAD_CONST (consti)

Pushes ``co_consts[consti]`` onto the stack.

.. opcode:: LOAD_NAME (namei)

Pushes the value associated with ``co_names[namei]`` onto the stack.

.. opcode:: BUILD_TUPLE (count)

Creates a tuple consuming *count* items from the stack, and pushes the
   resulting tuple onto the stack.

.. opcode:: BUILD_LIST (count)

Works as :opcode:`BUILD_TUPLE`, but creates a list.

.. opcode:: BUILD_SET (count)

Works as :opcode:`BUILD_TUPLE`, but creates a set.

.. opcode:: 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}``.

.. versionchanged:: 3.5
      The dictionary is created from stack items instead of creating an
      empty dictionary pre-sized to hold *count* items.

.. opcode:: BUILD_CONST_KEY_MAP (count)

The version of :opcode:`BUILD_MAP` specialized for constant keys.  *count*
   values are consumed from the stack.  The top element on the stack contains
   a tuple of keys.

.. versionadded:: 3.6

.. opcode:: BUILD_STRING (count)

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

.. versionadded:: 3.6

.. opcode:: BUILD_TUPLE_UNPACK (count)

Pops *count* iterables from the stack, joins them in a single tuple,
   and pushes the result.  Implements iterable unpacking in tuple
   displays ``(*x, *y, *z)``.

.. versionadded:: 3.5

.. opcode:: BUILD_TUPLE_UNPACK_WITH_CALL (count)

This is similar to :opcode:`BUILD_TUPLE_UNPACK`,
   but is used for ``f(*x, *y, *z)`` call syntax. The stack item at position
   ``count + 1`` should be the corresponding callable ``f``.

.. versionadded:: 3.6

.. opcode:: BUILD_LIST_UNPACK (count)

This is similar to :opcode:`BUILD_TUPLE_UNPACK`, but pushes a list
   instead of tuple.  Implements iterable unpacking in list
   displays ``[*x, *y, *z]``.

.. versionadded:: 3.5

.. opcode:: BUILD_SET_UNPACK (count)

This is similar to :opcode:`BUILD_TUPLE_UNPACK`, but pushes a set
   instead of tuple.  Implements iterable unpacking in set
   displays ``{*x, *y, *z}``.

.. versionadded:: 3.5

.. opcode:: BUILD_MAP_UNPACK (count)

Pops *count* mappings from the stack, merges them into a single dictionary,
   and pushes the result.  Implements dictionary unpacking in dictionary
   displays ``{**x, **y, **z}``.

.. versionadded:: 3.5

.. opcode:: BUILD_MAP_UNPACK_WITH_CALL (count)

This is similar to :opcode:`BUILD_MAP_UNPACK`,
   but is used for ``f(**x, **y, **z)`` call syntax.  The stack item at
   position ``count + 2`` should be the corresponding callable ``f``.

.. versionadded:: 3.5
   .. versionchanged:: 3.6
      The position of the callable is determined by adding 2 to the opcode
      argument instead of encoding it in the second byte of the argument.

.. opcode:: LOAD_ATTR (namei)

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

.. opcode:: COMPARE_OP (opname)

Performs a Boolean operation.  The operation name can be found in
   ``cmp_op[opname]``.

.. opcode:: IMPORT_NAME (namei)

Imports the module ``co_names[namei]``.  TOS and TOS1 are popped and provide
   the *fromlist* and *level* arguments of :func:`__import__`.  The module
   object is pushed onto the stack.  The current namespace is not affected: for
   a proper import statement, a subsequent :opcode:`STORE_FAST` instruction
   modifies the namespace.

.. opcode:: 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
   :opcode:`STORE_FAST` instruction.

.. opcode:: JUMP_FORWARD (delta)

Increments bytecode counter by *delta*.

.. opcode:: POP_JUMP_IF_TRUE (target)

If TOS is true, sets the bytecode counter to *target*.  TOS is popped.

.. versionadded:: 3.1

.. opcode:: POP_JUMP_IF_FALSE (target)

If TOS is false, sets the bytecode counter to *target*.  TOS is popped.

.. versionadded:: 3.1

.. opcode:: JUMP_IF_TRUE_OR_POP (target)

If TOS is true, sets the bytecode counter to *target* and leaves TOS on the
   stack.  Otherwise (TOS is false), TOS is popped.

.. versionadded:: 3.1

.. opcode:: JUMP_IF_FALSE_OR_POP (target)

If TOS is false, sets the bytecode counter to *target* and leaves TOS on the
   stack.  Otherwise (TOS is true), TOS is popped.

.. versionadded:: 3.1

.. opcode:: JUMP_ABSOLUTE (target)

Set bytecode counter to *target*.

.. opcode:: FOR_ITER (delta)

TOS is an :term:`iterator`.  Call its :meth:`~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 TOS is popped, and the byte
   code counter is incremented by *delta*.

.. opcode:: LOAD_GLOBAL (namei)

Loads the global named ``co_names[namei]`` onto the stack.

.. opcode:: SETUP_LOOP (delta)

Pushes a block for a loop onto the block stack.  The block spans from the
   current instruction with a size of *delta* bytes.

.. opcode:: SETUP_EXCEPT (delta)

Pushes a try block from a try-except clause onto the block stack. *delta*
   points to the first except block.

.. opcode:: SETUP_FINALLY (delta)

Pushes a try block from a try-except clause onto the block stack. *delta*
   points to the finally block.

.. opcode:: LOAD_FAST (var_num)

Pushes a reference to the local ``co_varnames[var_num]`` onto the stack.

.. opcode:: STORE_FAST (var_num)

Stores TOS into the local ``co_varnames[var_num]``.

.. opcode:: DELETE_FAST (var_num)

Deletes local ``co_varnames[var_num]``.

.. opcode:: STORE_ANNOTATION (namei)

Stores TOS as ``locals()['__annotations__'][co_names[namei]] = TOS``.

.. versionadded:: 3.6

.. opcode:: LOAD_CLOSURE (i)

Pushes a reference to the cell contained in slot *i* of the cell and free
   variable storage.  The name of the variable is ``co_cellvars[i]`` if *i* is
   less than the length of *co_cellvars*.  Otherwise it is ``co_freevars[i -
   len(co_cellvars)]``.

.. opcode:: LOAD_DEREF (i)

Loads the cell contained in slot *i* of the cell and free variable storage.
   Pushes a reference to the object the cell contains on the stack.

.. opcode:: LOAD_CLASSDEREF (i)

Much like :opcode:`LOAD_DEREF` but first checks the locals dictionary before
   consulting the cell.  This is used for loading free variables in class
   bodies.

.. versionadded:: 3.4

.. opcode:: STORE_DEREF (i)

Stores TOS into the cell contained in slot *i* of the cell and free variable
   storage.

.. opcode:: DELETE_DEREF (i)

Empties the cell contained in slot *i* of the cell and free variable storage.
   Used by the :keyword:`del` statement.

.. versionadded:: 3.2

.. opcode:: RAISE_VARARGS (argc)

Raises an exception. *argc* indicates the number of arguments to the raise
   statement, ranging from 0 to 3.  The handler will find the traceback as TOS2,
   the parameter as TOS1, and the exception as TOS.

.. opcode:: CALL_FUNCTION (argc)

Calls a callable object with positional arguments.
   *argc* indicates the number of positional arguments.
   The top of the stack contains positional arguments, with the right-most
   argument on top.  Below the arguments is a callable object to call.
   ``CALL_FUNCTION`` 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.

.. versionchanged:: 3.6
      This opcode is used only for calls with positional arguments.

.. opcode:: CALL_FUNCTION_KW (argc)

Calls a callable object with positional (if any) and keyword arguments.
   *argc* indicates the total number of positional and keyword arguments.
   The top element on the stack contains a tuple of keyword argument names.
   Below that are keyword arguments in the order corresponding to the tuple.
   Below that are positional arguments, with the right-most parameter on
   top.  Below the arguments is a callable object to call.
   ``CALL_FUNCTION_KW`` 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.

.. versionchanged:: 3.6
      Keyword arguments are packed in a tuple instead of a dictionary,
      *argc* indicates the total number of arguments.

.. opcode:: 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.
   Below that is an iterable object containing positional arguments and
   a callable object to call.  :opcode:`BUILD_MAP_UNPACK_WITH_CALL` and
   :opcode:`BUILD_TUPLE_UNPACK_WITH_CALL` can be used for merging multiple
   mapping objects and iterables containing 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.

.. versionadded:: 3.6

.. opcode:: MAKE_FUNCTION (argc)

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`` an annotation dictionary
   * ``0x08`` a tuple containing cells for free variables, making a closure
   * the code associated with the function (at TOS1)
   * the :term:`qualified name` of the function (at TOS)

.. opcode:: BUILD_SLICE (argc)

.. index:: builtin: slice

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 :func:`slice` built-in function for more information.

.. opcode:: EXTENDED_ARG (ext)

Prefixes any opcode which has an argument too big to fit into the default two
   bytes.  *ext* holds two additional bytes which, taken together with the
   subsequent opcode's argument, comprise a four-byte argument, *ext* being the
   two most-significant bytes.

.. opcode:: 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 :func:`str` on *value* before
     formatting it.
   * ``(flags & 0x03) == 0x02``: call :func:`repr` on *value* before
     formatting it.
   * ``(flags & 0x03) == 0x03``: call :func:`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 :c:func:`PyObject_Format`.  The
   result is pushed on the stack.

.. versionadded:: 3.6

.. opcode:: 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).

.. versionchanged:: 3.6
      Now every instruction has an argument, but opcodes ``< HAVE_ARGUMENT``
      ignore it. Before, only opcodes ``>= HAVE_ARGUMENT`` had an argument.

.. _opcode_collections:

Opcode collections
------------------

These collections are provided for automatic introspection of bytecode
instructions:

.. data:: opname

Sequence of operation names, indexable using the bytecode.

.. data:: opmap

Dictionary mapping operation names to bytecodes.

.. data:: cmp_op

Sequence of all compare operation names.

.. data:: hasconst

Sequence of bytecodes that access a constant.

.. data:: 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).

.. data:: hasname

Sequence of bytecodes that access an attribute by name.

.. data:: hasjrel

Sequence of bytecodes that have a relative jump target.

.. data:: hasjabs

Sequence of bytecodes that have an absolute jump target.

.. data:: haslocal

Sequence of bytecodes that access a local variable.

.. data:: hascompare

Sequence of bytecodes of Boolean operations.

:mod:`dis` --- Disassembler for Python bytecode =============================================== .. module:: dis :synopsis: Disassembler for Python bytecode. **Source code:** :source:`Lib/dis.py` -------------- The :mod:`dis` module supports the analysis of CPython :term:`bytecode` by disassembling it. The CPython bytecode which this module takes as an input is defined in the file :file:`Include/opcode.h` and used by the compiler and the interpreter. .. impl-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. .. versionchanged:: 3.6 Use 2 bytes for each instruction. Previously the number of bytes varied by instruction. Example: Given the function :func:`myfunc`:: def myfunc(alist): return len(alist) the following command can be used to display the disassembly of :func:`myfunc`:: >>> dis.dis(myfunc) 2 0 LOAD_GLOBAL 0 (len) 2 LOAD_FAST 0 (alist) 4 CALL_FUNCTION 1 6 RETURN_VALUE (The "2" is a line number). Bytecode analysis ----------------- .. versionadded:: 3.4 The bytecode analysis API allows pieces of Python code to be wrapped in a :class:`Bytecode` object that provides easy access to details of the compiled code. .. class:: Bytecode(x, *, first_line=None, current_offset=None) Analyse the bytecode corresponding to a function, generator, method, string of source code, or a code object (as returned by :func:`compile`). This is a convenience wrapper around many of the functions listed below, most notably :func:`get_instructions`, as iterating over a :class:`Bytecode` instance yields the bytecode operations as :class:`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 :meth:`.dis` will display a "current instruction" marker against the specified opcode. .. classmethod:: from_traceback(tb) Construct a :class:`Bytecode` instance from the given traceback, setting *current_offset* to the instruction responsible for the exception. .. data:: codeobj The compiled code object. .. data:: first_line The first source line of the code object (if available) .. method:: dis() Return a formatted view of the bytecode operations (the same as printed by :func:`dis.dis`, but returned as a multi-line string). .. method:: info() Return a formatted multi-line string with detailed information about the code object, like :func:`code_info`. Example:: >>> bytecode = dis.Bytecode(myfunc) >>> for instr in bytecode: ... print(instr.opname) ... LOAD_GLOBAL LOAD_FAST CALL_FUNCTION RETURN_VALUE Analysis functions ------------------ The :mod:`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: .. function:: code_info(x) Return a formatted multi-line string with detailed code object information for the supplied function, generator, 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. .. versionadded:: 3.2 .. function:: 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. .. versionadded:: 3.2 .. versionchanged:: 3.4 Added *file* parameter. .. function:: dis(x=None, *, file=None) Disassemble the *x* object. *x* can denote either a module, a class, a method, a function, a generator, 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. Strings are first compiled to code objects with the :func:`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. .. versionchanged:: 3.4 Added *file* parameter. .. function:: distb(tb=None, *, file=None) 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. .. versionchanged:: 3.4 Added *file* parameter. .. function:: disassemble(code, lasti=-1, *, file=None) disco(code, lasti=-1, *, file=None) 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. .. versionchanged:: 3.4 Added *file* parameter. .. function:: get_instructions(x, *, first_line=None) Return an iterator over the instructions in the supplied function, method, source code string or code object. The iterator generates a series of :class:`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. .. versionadded:: 3.4 .. function:: findlinestarts(code) This generator function uses the ``co_firstlineno`` and ``co_lnotab`` attributes 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. See :source:`Objects/lnotab_notes.txt` for the ``co_lnotab`` format and how to decode it. .. versionchanged:: 3.6 Line numbers can be decreasing. Before, they were always increasing. .. function:: findlabels(code) Detect all offsets in the code object *code* which are jump targets, and return a list of these offsets. .. function:: stack_effect(opcode, [oparg]) Compute the stack effect of *opcode* with argument *oparg*. .. versionadded:: 3.4 .. _bytecodes: Python Bytecode Instructions ---------------------------- The :func:`get_instructions` function and :class:`Bytecode` class provide details of bytecode instructions as :class:`Instruction` instances: .. class:: Instruction Details for a bytecode operation .. data:: opcode numeric code for operation, corresponding to the opcode values listed below and the bytecode values in the :ref:`opcode_collections`. .. data:: opname human readable name for operation .. data:: arg numeric argument to operation (if any), otherwise ``None`` .. data:: argval resolved arg value (if known), otherwise same as arg .. data:: argrepr human readable description of operation argument .. data:: offset start index of operation within bytecode sequence .. data:: starts_line line started by this opcode (if any), otherwise ``None`` .. data:: is_jump_target ``True`` if other code jumps to here, otherwise ``False`` .. versionadded:: 3.4 The Python compiler currently generates the following bytecode instructions. **General instructions** .. opcode:: NOP Do nothing code. Used as a placeholder by the bytecode optimizer. .. opcode:: POP_TOP Removes the top-of-stack (TOS) item. .. opcode:: ROT_TWO Swaps the two top-most stack items. .. opcode:: ROT_THREE Lifts second and third stack item one position up, moves top down to position three. .. opcode:: DUP_TOP Duplicates the reference on top of the stack. .. versionadded:: 3.2 .. opcode:: DUP_TOP_TWO Duplicates the two references on top of the stack, leaving them in the same order. .. versionadded:: 3.2 **Unary operations** Unary operations take the top of the stack, apply the operation, and push the result back on the stack. .. opcode:: UNARY_POSITIVE Implements ``TOS = +TOS``. .. opcode:: UNARY_NEGATIVE Implements ``TOS = -TOS``. .. opcode:: UNARY_NOT Implements ``TOS = not TOS``. .. opcode:: UNARY_INVERT Implements ``TOS = ~TOS``. .. opcode:: GET_ITER Implements ``TOS = iter(TOS)``. .. opcode:: GET_YIELD_FROM_ITER If ``TOS`` is a :term:`generator iterator` or :term:`coroutine` object it is left as is. Otherwise, implements ``TOS = iter(TOS)``. .. versionadded:: 3.5 **Binary 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. .. opcode:: BINARY_POWER Implements ``TOS = TOS1 ** TOS``. .. opcode:: BINARY_MULTIPLY Implements ``TOS = TOS1 * TOS``. .. opcode:: BINARY_MATRIX_MULTIPLY Implements ``TOS = TOS1 @ TOS``. .. versionadded:: 3.5 .. opcode:: BINARY_FLOOR_DIVIDE Implements ``TOS = TOS1 // TOS``. .. opcode:: BINARY_TRUE_DIVIDE Implements ``TOS = TOS1 / TOS``. .. opcode:: BINARY_MODULO Implements ``TOS = TOS1 % TOS``. .. opcode:: BINARY_ADD Implements ``TOS = TOS1 + TOS``. .. opcode:: BINARY_SUBTRACT Implements ``TOS = TOS1 - TOS``. .. opcode:: BINARY_SUBSCR Implements ``TOS = TOS1[TOS]``. .. opcode:: BINARY_LSHIFT Implements ``TOS = TOS1 << TOS``. .. opcode:: BINARY_RSHIFT Implements ``TOS = TOS1 >> TOS``. .. opcode:: BINARY_AND Implements ``TOS = TOS1 & TOS``. .. opcode:: BINARY_XOR Implements ``TOS = TOS1 ^ TOS``. .. opcode:: BINARY_OR Implements ``TOS = TOS1 | TOS``. **In-place operations** 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. .. opcode:: INPLACE_POWER Implements in-place ``TOS = TOS1 ** TOS``. .. opcode:: INPLACE_MULTIPLY Implements in-place ``TOS = TOS1 * TOS``. .. opcode:: INPLACE_MATRIX_MULTIPLY Implements in-place ``TOS = TOS1 @ TOS``. .. versionadded:: 3.5 .. opcode:: INPLACE_FLOOR_DIVIDE Implements in-place ``TOS = TOS1 // TOS``. .. opcode:: INPLACE_TRUE_DIVIDE Implements in-place ``TOS = TOS1 / TOS``. .. opcode:: INPLACE_MODULO Implements in-place ``TOS = TOS1 % TOS``. .. opcode:: INPLACE_ADD Implements in-place ``TOS = TOS1 + TOS``. .. opcode:: INPLACE_SUBTRACT Implements in-place ``TOS = TOS1 - TOS``. .. opcode:: INPLACE_LSHIFT Implements in-place ``TOS = TOS1 << TOS``. .. opcode:: INPLACE_RSHIFT Implements in-place ``TOS = TOS1 >> TOS``. .. opcode:: INPLACE_AND Implements in-place ``TOS = TOS1 & TOS``. .. opcode:: INPLACE_XOR Implements in-place ``TOS = TOS1 ^ TOS``. .. opcode:: INPLACE_OR Implements in-place ``TOS = TOS1 | TOS``. .. opcode:: STORE_SUBSCR Implements ``TOS1[TOS] = TOS2``. .. opcode:: DELETE_SUBSCR Implements ``del TOS1[TOS]``. **Coroutine opcodes** .. opcode:: GET_AWAITABLE 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__``. .. versionadded:: 3.5 .. opcode:: GET_AITER Implements ``TOS = get_awaitable(TOS.__aiter__())``. See ``GET_AWAITABLE`` for details about ``get_awaitable`` .. versionadded:: 3.5 .. opcode:: GET_ANEXT Implements ``PUSH(get_awaitable(TOS.__anext__()))``. See ``GET_AWAITABLE`` for details about ``get_awaitable`` .. versionadded:: 3.5 .. opcode:: BEFORE_ASYNC_WITH Resolves ``__aenter__`` and ``__aexit__`` from the object on top of the stack. Pushes ``__aexit__`` and result of ``__aenter__()`` to the stack. .. versionadded:: 3.5 .. opcode:: SETUP_ASYNC_WITH Creates a new frame object. .. versionadded:: 3.5 **Miscellaneous opcodes** .. opcode:: 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 :opcode:`POP_TOP`. .. opcode:: BREAK_LOOP Terminates a loop due to a :keyword:`break` statement. .. opcode:: CONTINUE_LOOP (target) Continues a loop due to a :keyword:`continue` statement. *target* is the address to jump to (which should be a :opcode:`FOR_ITER` instruction). .. opcode:: SET_ADD (i) Calls ``set.add(TOS1[-i], TOS)``. Used to implement set comprehensions. .. opcode:: LIST_APPEND (i) Calls ``list.append(TOS[-i], TOS)``. Used to implement list comprehensions. .. opcode:: MAP_ADD (i) Calls ``dict.setitem(TOS1[-i], TOS, TOS1)``. Used to implement dict comprehensions. .. versionadded:: 3.1 For all of the :opcode:`SET_ADD`, :opcode:`LIST_APPEND` and :opcode:`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. .. opcode:: RETURN_VALUE Returns with TOS to the caller of the function. .. opcode:: YIELD_VALUE Pops TOS and yields it from a :term:`generator`. .. opcode:: YIELD_FROM Pops TOS and delegates to it as a subiterator from a :term:`generator`. .. versionadded:: 3.3 .. opcode:: 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 :term:`variable annotations ` statically. .. versionadded:: 3.6 .. opcode:: 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 *``. .. opcode:: POP_BLOCK Removes one block from the block stack. Per frame, there is a stack of blocks, denoting nested loops, try statements, and such. .. opcode:: POP_EXCEPT Removes one block from the block stack. The popped block must be an exception handler block, as implicitly created when entering an except handler. In addition to popping extraneous values from the frame stack, the last three popped values are used to restore the exception state. .. opcode:: END_FINALLY Terminates a :keyword:`finally` clause. The interpreter recalls whether the exception has to be re-raised, or whether the function returns, and continues with the outer-next block. .. opcode:: LOAD_BUILD_CLASS Pushes :func:`builtins.__build_class__` onto the stack. It is later called by :opcode:`CALL_FUNCTION` to construct a class. .. opcode:: SETUP_WITH (delta) This opcode performs several operations before a with block starts. First, it loads :meth:`~object.__exit__` from the context manager and pushes it onto the stack for later use by :opcode:`WITH_CLEANUP`. Then, :meth:`~object.__enter__` is called, and a finally block pointing to *delta* is pushed. Finally, the result of calling the enter method is pushed onto the stack. The next opcode will either ignore it (:opcode:`POP_TOP`), or store it in (a) variable(s) (:opcode:`STORE_FAST`, :opcode:`STORE_NAME`, or :opcode:`UNPACK_SEQUENCE`). .. versionadded:: 3.2 .. opcode:: WITH_CLEANUP_START Cleans up the stack when a :keyword:`with` statement block exits. TOS is the context manager's :meth:`__exit__` bound method. Below TOS are 1--3 values indicating how/why the finally clause was entered: * SECOND = ``None`` * (SECOND, THIRD) = (``WHY_{RETURN,CONTINUE}``), retval * SECOND = ``WHY_*``; no retval below it * (SECOND, THIRD, FOURTH) = exc_info() In the last case, ``TOS(SECOND, THIRD, FOURTH)`` is called, otherwise ``TOS(None, None, None)``. Pushes SECOND and result of the call to the stack. .. opcode:: WITH_CLEANUP_FINISH Pops exception type and result of 'exit' function call from the stack. If the stack represents an exception, *and* the function call returns a 'true' value, this information is "zapped" and replaced with a single ``WHY_SILENCED`` to prevent :opcode:`END_FINALLY` from re-raising the exception. (But non-local gotos will still be resumed.) .. XXX explain the WHY stuff! All of the following opcodes use their arguments. .. opcode:: STORE_NAME (namei) Implements ``name = TOS``. *namei* is the index of *name* in the attribute :attr:`co_names` of the code object. The compiler tries to use :opcode:`STORE_FAST` or :opcode:`STORE_GLOBAL` if possible. .. opcode:: DELETE_NAME (namei) Implements ``del name``, where *namei* is the index into :attr:`co_names` attribute of the code object. .. opcode:: UNPACK_SEQUENCE (count) Unpacks TOS into *count* individual values, which are put onto the stack right-to-left. .. opcode:: 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. .. opcode:: STORE_ATTR (namei) Implements ``TOS.name = TOS1``, where *namei* is the index of name in :attr:`co_names`. .. opcode:: DELETE_ATTR (namei) Implements ``del TOS.name``, using *namei* as index into :attr:`co_names`. .. opcode:: STORE_GLOBAL (namei) Works as :opcode:`STORE_NAME`, but stores the name as a global. .. opcode:: DELETE_GLOBAL (namei) Works as :opcode:`DELETE_NAME`, but deletes a global name. .. opcode:: LOAD_CONST (consti) Pushes ``co_consts[consti]`` onto the stack. .. opcode:: LOAD_NAME (namei) Pushes the value associated with ``co_names[namei]`` onto the stack. .. opcode:: BUILD_TUPLE (count) Creates a tuple consuming *count* items from the stack, and pushes the resulting tuple onto the stack. .. opcode:: BUILD_LIST (count) Works as :opcode:`BUILD_TUPLE`, but creates a list. .. opcode:: BUILD_SET (count) Works as :opcode:`BUILD_TUPLE`, but creates a set. .. opcode:: 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}``. .. versionchanged:: 3.5 The dictionary is created from stack items instead of creating an empty dictionary pre-sized to hold *count* items. .. opcode:: BUILD_CONST_KEY_MAP (count) The version of :opcode:`BUILD_MAP` specialized for constant keys. *count* values are consumed from the stack. The top element on the stack contains a tuple of keys. .. versionadded:: 3.6 .. opcode:: BUILD_STRING (count) Concatenates *count* strings from the stack and pushes the resulting string onto the stack. .. versionadded:: 3.6 .. opcode:: BUILD_TUPLE_UNPACK (count) Pops *count* iterables from the stack, joins them in a single tuple, and pushes the result. Implements iterable unpacking in tuple displays ``(*x, *y, *z)``. .. versionadded:: 3.5 .. opcode:: BUILD_TUPLE_UNPACK_WITH_CALL (count) This is similar to :opcode:`BUILD_TUPLE_UNPACK`, but is used for ``f(*x, *y, *z)`` call syntax. The stack item at position ``count + 1`` should be the corresponding callable ``f``. .. versionadded:: 3.6 .. opcode:: BUILD_LIST_UNPACK (count) This is similar to :opcode:`BUILD_TUPLE_UNPACK`, but pushes a list instead of tuple. Implements iterable unpacking in list displays ``[*x, *y, *z]``. .. versionadded:: 3.5 .. opcode:: BUILD_SET_UNPACK (count) This is similar to :opcode:`BUILD_TUPLE_UNPACK`, but pushes a set instead of tuple. Implements iterable unpacking in set displays ``{*x, *y, *z}``. .. versionadded:: 3.5 .. opcode:: BUILD_MAP_UNPACK (count) Pops *count* mappings from the stack, merges them into a single dictionary, and pushes the result. Implements dictionary unpacking in dictionary displays ``{**x, **y, **z}``. .. versionadded:: 3.5 .. opcode:: BUILD_MAP_UNPACK_WITH_CALL (count) This is similar to :opcode:`BUILD_MAP_UNPACK`, but is used for ``f(**x, **y, **z)`` call syntax. The stack item at position ``count + 2`` should be the corresponding callable ``f``. .. versionadded:: 3.5 .. versionchanged:: 3.6 The position of the callable is determined by adding 2 to the opcode argument instead of encoding it in the second byte of the argument. .. opcode:: LOAD_ATTR (namei) Replaces TOS with ``getattr(TOS, co_names[namei])``. .. opcode:: COMPARE_OP (opname) Performs a Boolean operation. The operation name can be found in ``cmp_op[opname]``. .. opcode:: IMPORT_NAME (namei) Imports the module ``co_names[namei]``. TOS and TOS1 are popped and provide the *fromlist* and *level* arguments of :func:`__import__`. The module object is pushed onto the stack. The current namespace is not affected: for a proper import statement, a subsequent :opcode:`STORE_FAST` instruction modifies the namespace. .. opcode:: 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 :opcode:`STORE_FAST` instruction. .. opcode:: JUMP_FORWARD (delta) Increments bytecode counter by *delta*. .. opcode:: POP_JUMP_IF_TRUE (target) If TOS is true, sets the bytecode counter to *target*. TOS is popped. .. versionadded:: 3.1 .. opcode:: POP_JUMP_IF_FALSE (target) If TOS is false, sets the bytecode counter to *target*. TOS is popped. .. versionadded:: 3.1 .. opcode:: JUMP_IF_TRUE_OR_POP (target) If TOS is true, sets the bytecode counter to *target* and leaves TOS on the stack. Otherwise (TOS is false), TOS is popped. .. versionadded:: 3.1 .. opcode:: JUMP_IF_FALSE_OR_POP (target) If TOS is false, sets the bytecode counter to *target* and leaves TOS on the stack. Otherwise (TOS is true), TOS is popped. .. versionadded:: 3.1 .. opcode:: JUMP_ABSOLUTE (target) Set bytecode counter to *target*. .. opcode:: FOR_ITER (delta) TOS is an :term:`iterator`. Call its :meth:`~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 TOS is popped, and the byte code counter is incremented by *delta*. .. opcode:: LOAD_GLOBAL (namei) Loads the global named ``co_names[namei]`` onto the stack. .. opcode:: SETUP_LOOP (delta) Pushes a block for a loop onto the block stack. The block spans from the current instruction with a size of *delta* bytes. .. opcode:: SETUP_EXCEPT (delta) Pushes a try block from a try-except clause onto the block stack. *delta* points to the first except block. .. opcode:: SETUP_FINALLY (delta) Pushes a try block from a try-except clause onto the block stack. *delta* points to the finally block. .. opcode:: LOAD_FAST (var_num) Pushes a reference to the local ``co_varnames[var_num]`` onto the stack. .. opcode:: STORE_FAST (var_num) Stores TOS into the local ``co_varnames[var_num]``. .. opcode:: DELETE_FAST (var_num) Deletes local ``co_varnames[var_num]``. .. opcode:: STORE_ANNOTATION (namei) Stores TOS as ``locals()['__annotations__'][co_names[namei]] = TOS``. .. versionadded:: 3.6 .. opcode:: LOAD_CLOSURE (i) Pushes a reference to the cell contained in slot *i* of the cell and free variable storage. The name of the variable is ``co_cellvars[i]`` if *i* is less than the length of *co_cellvars*. Otherwise it is ``co_freevars[i - len(co_cellvars)]``. .. opcode:: LOAD_DEREF (i) Loads the cell contained in slot *i* of the cell and free variable storage. Pushes a reference to the object the cell contains on the stack. .. opcode:: LOAD_CLASSDEREF (i) Much like :opcode:`LOAD_DEREF` but first checks the locals dictionary before consulting the cell. This is used for loading free variables in class bodies. .. versionadded:: 3.4 .. opcode:: STORE_DEREF (i) Stores TOS into the cell contained in slot *i* of the cell and free variable storage. .. opcode:: DELETE_DEREF (i) Empties the cell contained in slot *i* of the cell and free variable storage. Used by the :keyword:`del` statement. .. versionadded:: 3.2 .. opcode:: RAISE_VARARGS (argc) Raises an exception. *argc* indicates the number of arguments to the raise statement, ranging from 0 to 3. The handler will find the traceback as TOS2, the parameter as TOS1, and the exception as TOS. .. opcode:: CALL_FUNCTION (argc) Calls a callable object with positional arguments. *argc* indicates the number of positional arguments. The top of the stack contains positional arguments, with the right-most argument on top. Below the arguments is a callable object to call. ``CALL_FUNCTION`` 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. .. versionchanged:: 3.6 This opcode is used only for calls with positional arguments. .. opcode:: CALL_FUNCTION_KW (argc) Calls a callable object with positional (if any) and keyword arguments. *argc* indicates the total number of positional and keyword arguments. The top element on the stack contains a tuple of keyword argument names. Below that are keyword arguments in the order corresponding to the tuple. Below that are positional arguments, with the right-most parameter on top. Below the arguments is a callable object to call. ``CALL_FUNCTION_KW`` 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. .. versionchanged:: 3.6 Keyword arguments are packed in a tuple instead of a dictionary, *argc* indicates the total number of arguments. .. opcode:: 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. Below that is an iterable object containing positional arguments and a callable object to call. :opcode:`BUILD_MAP_UNPACK_WITH_CALL` and :opcode:`BUILD_TUPLE_UNPACK_WITH_CALL` can be used for merging multiple mapping objects and iterables containing 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. .. versionadded:: 3.6 .. opcode:: MAKE_FUNCTION (argc) 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`` an annotation dictionary * ``0x08`` a tuple containing cells for free variables, making a closure * the code associated with the function (at TOS1) * the :term:`qualified name` of the function (at TOS) .. opcode:: BUILD_SLICE (argc) .. index:: builtin: slice 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 :func:`slice` built-in function for more information. .. opcode:: EXTENDED_ARG (ext) Prefixes any opcode which has an argument too big to fit into the default two bytes. *ext* holds two additional bytes which, taken together with the subsequent opcode's argument, comprise a four-byte argument, *ext* being the two most-significant bytes. .. opcode:: 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 :func:`str` on *value* before formatting it. * ``(flags & 0x03) == 0x02``: call :func:`repr` on *value* before formatting it. * ``(flags & 0x03) == 0x03``: call :func:`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 :c:func:`PyObject_Format`. The result is pushed on the stack. .. versionadded:: 3.6 .. opcode:: 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). .. versionchanged:: 3.6 Now every instruction has an argument, but opcodes ``< HAVE_ARGUMENT`` ignore it. Before, only opcodes ``>= HAVE_ARGUMENT`` had an argument. .. _opcode_collections: Opcode collections ------------------ These collections are provided for automatic introspection of bytecode instructions: .. data:: opname Sequence of operation names, indexable using the bytecode. .. data:: opmap Dictionary mapping operation names to bytecodes. .. data:: cmp_op Sequence of all compare operation names. .. data:: hasconst Sequence of bytecodes that access a constant. .. data:: 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). .. data:: hasname Sequence of bytecodes that access an attribute by name. .. data:: hasjrel Sequence of bytecodes that have a relative jump target. .. data:: hasjabs Sequence of bytecodes that have an absolute jump target. .. data:: haslocal Sequence of bytecodes that access a local variable. .. data:: hascompare Sequence of bytecodes of Boolean operations.