: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, asynchronous generator, coroutine, 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`. .. versionchanged:: 3.7 This can now handle coroutine and asynchronous generator objects. 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, 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. .. versionadded:: 3.2 .. versionchanged:: 3.7 This can now handle coroutine and asynchronous generator objects. .. 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, depth=None) 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 :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. The maximal depth of recursion is limited by *depth* unless it is ``None``. ``depth=0`` means no recursion. .. versionchanged:: 3.4 Added *file* parameter. .. versionchanged:: 3.7 Implemented recursive disassembling and added *depth* parameter. .. versionchanged:: 3.7 This can now handle coroutine and asynchronous generator objects. .. 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 raw compiled bytecode string *code* which are jump targets, and return a list of these offsets. .. function:: 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``, :func:`~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. .. versionadded:: 3.4 .. versionchanged:: 3.8 Added *jump* parameter. .. _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 any), otherwise ``None`` .. data:: argrepr human readable description of operation argument (if any), otherwise an empty string. .. 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:: ROT_FOUR Lifts second, third and fourth stack items one position up, moves top down to position four. .. versionadded:: 3.8 .. 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 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. .. opcode:: BINARY_OP (op) Implements the binary and in-place operators (depending on the value of *op*). .. versionadded:: 3.11 .. opcode:: BINARY_SUBSCR Implements ``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 = TOS.__aiter__()``. .. versionadded:: 3.5 .. versionchanged:: 3.7 Returning awaitable objects from ``__aiter__`` is no longer supported. .. opcode:: GET_ANEXT Implements ``PUSH(get_awaitable(TOS.__anext__()))``. See ``GET_AWAITABLE`` for details about ``get_awaitable`` .. versionadded:: 3.5 .. opcode:: END_ASYNC_FOR Terminates an :keyword:`async for` loop. Handles an exception raised when awaiting a next item. If TOS is :exc:`StopAsyncIteration` pop 7 values from the stack and restore the exception state using the second three of them. Otherwise re-raise the exception using the three values from the stack. An exception handler block is removed from the block stack. .. versionadded:: 3.8 .. 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 **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:: SET_ADD (i) Calls ``set.add(TOS1[-i], TOS)``. Used to implement set comprehensions. .. opcode:: LIST_APPEND (i) Calls ``list.append(TOS1[-i], TOS)``. Used to implement list comprehensions. .. opcode:: MAP_ADD (i) Calls ``dict.__setitem__(TOS1[-i], TOS1, TOS)``. Used to implement dict comprehensions. .. versionadded:: 3.1 .. versionchanged:: 3.8 Map value is TOS and map key is TOS1. Before, those were reversed. 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_EXCEPT Pops three values from the stack, which are used to restore the exception state. .. opcode:: 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. .. versionadded:: 3.9 .. opcode:: PUSH_EXC_INFO Pops the three values from the stack. Pushes the current exception to the top of the stack. Pushes the three values originally popped back to the stack. Used in exception handlers. .. versionadded:: 3.11 .. opcode:: WITH_EXCEPT_START Calls the function in position 7 on the stack with the top three items on the stack as arguments. Used to implement the call ``context_manager.__exit__(*exc_info())`` when an exception has occurred in a :keyword:`with` statement. .. versionadded:: 3.9 .. opcode:: POP_EXCEPT_AND_RERAISE Pops the exception currently on top of the stack. Pops the integer value on top of the stack and sets the ``f_lasti`` attribute of the frame with that value. Then pops the next exception from the stack uses it to restore the current exception. Finally it re-raises the originally popped exception. Used in exception handler cleanup. .. versionadded:: 3.11 .. opcode:: LOAD_ASSERTION_ERROR Pushes :exc:`AssertionError` onto the stack. Used by the :keyword:`assert` statement. .. versionadded:: 3.9 .. 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:: BEFORE_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_EXCEPT_START`. Then, :meth:`~object.__enter__` is called. Finally, the result of calling the ``__enter__()`` method is pushed onto the stack. .. versionadded:: 3.11 .. opcode:: GET_LEN Push ``len(TOS)`` onto the stack. .. versionadded:: 3.10 .. opcode:: MATCH_MAPPING If TOS is an instance of :class:`collections.abc.Mapping` (or, more technically: if it has the :const:`Py_TPFLAGS_MAPPING` flag set in its :c:member:`~PyTypeObject.tp_flags`), push ``True`` onto the stack. Otherwise, push ``False``. .. versionadded:: 3.10 .. opcode:: MATCH_SEQUENCE If TOS is an instance of :class:`collections.abc.Sequence` and is *not* an instance of :class:`str`/:class:`bytes`/:class:`bytearray` (or, more technically: if it has the :const:`Py_TPFLAGS_SEQUENCE` flag set in its :c:member:`~PyTypeObject.tp_flags`), push ``True`` onto the stack. Otherwise, push ``False``. .. versionadded:: 3.10 .. opcode:: 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 :class:`tuple` containing the corresponding values. Otherwise, push ``None``. .. versionadded:: 3.10 .. versionchanged:: 3.11 Previously, this instruction also pushed a boolean value indicating success (``True``) or failure (``False``). 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. 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. .. 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:: LIST_TO_TUPLE Pops a list from the stack and pushes a tuple containing the same values. .. versionadded:: 3.9 .. opcode:: LIST_EXTEND (i) Calls ``list.extend(TOS1[-i], TOS)``. Used to build lists. .. versionadded:: 3.9 .. opcode:: SET_UPDATE (i) Calls ``set.update(TOS1[-i], TOS)``. Used to build sets. .. versionadded:: 3.9 .. opcode:: DICT_UPDATE (i) Calls ``dict.update(TOS1[-i], TOS)``. Used to build dicts. .. versionadded:: 3.9 .. opcode:: DICT_MERGE (i) Like :opcode:`DICT_UPDATE` but raises an exception for duplicate keys. .. versionadded:: 3.9 .. 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:: IS_OP (invert) Performs ``is`` comparison, or ``is not`` if ``invert`` is 1. .. versionadded:: 3.9 .. opcode:: CONTAINS_OP (invert) Performs ``in`` comparison, or ``not in`` if ``invert`` is 1. .. versionadded:: 3.9 .. 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_NOT_EXC_MATCH (target) Tests whether the second value on the stack is an exception matching TOS, and jumps if it is not. Pops one value from the stack. .. versionadded:: 3.9 .. versionchanged:: 3.11 This opcode no longer pops the active exception. .. 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:: 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:: MAKE_CELL (i) Creates a new cell in slot ``i``. If that slot is empty then that value is stored into the new cell. .. versionadded:: 3.11 .. opcode:: 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. .. versionchanged:: 3.11 ``i`` is no longer offset by the length of ``co_varnames``. .. opcode:: 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. .. versionchanged:: 3.11 ``i`` is no longer offset by the length of ``co_varnames``. .. 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 .. versionchanged:: 3.11 ``i`` is no longer offset by the length of ``co_varnames``. .. opcode:: STORE_DEREF (i) Stores TOS into the cell contained in slot ``i`` of the "fast locals" storage. .. versionchanged:: 3.11 ``i`` is no longer offset by the length of ``co_varnames``. .. opcode:: DELETE_DEREF (i) Empties the cell contained in slot ``i`` of the "fast locals" storage. Used by the :keyword:`del` statement. .. versionadded:: 3.2 .. versionchanged:: 3.11 ``i`` is no longer offset by the length of ``co_varnames``. .. opcode:: 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. .. versionadded:: 3.11 .. opcode:: 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``) .. 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 with the names of the keyword arguments, which must be strings. Below that are the values for the 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. 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:: 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 :opcode:`CALL_METHOD` when calling the unbound method. Otherwise, ``NULL`` and the object return by the attribute lookup are pushed. .. versionadded:: 3.7 .. opcode:: CALL_METHOD (argc) Calls a method. *argc* is the number of positional arguments. Keyword arguments are not supported. This opcode is designed to be used with :opcode:`LOAD_METHOD`. Positional arguments are on top of the stack. Below them, the two items described in :opcode:`LOAD_METHOD` are on the stack (either ``self`` and an unbound method object or ``NULL`` and an arbitrary callable). All of them are popped and the return value is pushed. .. versionadded:: 3.7 .. opcode:: CALL_METHOD_KW (argc) Calls a method in a similar fashion as :opcode:`CALL_METHOD`, but also supports keyword arguments. *argc* is the number of positional and keyword arguments. This opcode is designed to be used with :opcode:`LOAD_METHOD`. TOS is a tuple of keyword argument names. Argument values are below that. Below them, the two items described in :opcode:`LOAD_METHOD` are on the stack (either ``self`` and an unbound method object or ``NULL`` and an arbitrary callable). All of them are popped from the stack and the return value is pushed. .. versionadded:: 3.11 .. opcode:: 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 TOS1) * the :term:`qualified name` of the function (at TOS) .. versionchanged:: 3.10 Flag value ``0x04`` is a tuple of strings instead of dictionary .. 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 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. .. 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:: 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``. .. versionadded:: 3.10 .. versionchanged:: 3.11 Previously, this instruction also pushed a boolean value indicating success (``True``) or failure (``False``). .. opcode:: GEN_START (kind) Pops TOS. If TOS was not ``None``, raises an exception. The ``kind`` operand corresponds to the type of generator or coroutine and determines the error message. The legal kinds are 0 for generator, 1 for coroutine, and 2 for async generator. .. versionadded:: 3.10 .. opcode:: ROT_N (count) Lift the top *count* stack items one position up, and move TOS down to position *count*. .. versionadded:: 3.10 .. opcode:: COPY (i) Push the *i*-th item to the top of the stack. The item is not removed from its original location. .. versionadded:: 3.11 .. 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.