Code Objects

Code objects are a low-level detail of the CPython implementation. Each one represents a chunk of executable code that hasn’t yet been bound into a function.

type PyCodeObject

The C structure of the objects used to describe code objects. The fields of this type are subject to change at any time.

PyTypeObject PyCode_Type

This is an instance of PyTypeObject representing the Python code type.

int PyCode_Check(PyObject *co)

Return true if co is a code object. This function always succeeds.

int PyCode_GetNumFree(PyCodeObject *co)

Return the number of free variables in co.

PyCodeObject *PyCode_New(int argcount, int kwonlyargcount, int nlocals, int stacksize, int flags, PyObject *code, PyObject *consts, PyObject *names, PyObject *varnames, PyObject *freevars, PyObject *cellvars, PyObject *filename, PyObject *name, int firstlineno, PyObject *linetable, PyObject *exceptiontable)

Return value: New reference.

Return a new code object. If you need a dummy code object to create a frame, use PyCode_NewEmpty() instead. Calling PyCode_New() directly will bind you to a precise Python version since the definition of the bytecode changes often. The many arguments of this function are inter-dependent in complex ways, meaning that subtle changes to values are likely to result in incorrect execution or VM crashes. Use this function only with extreme care.

Changed in version 3.11: Added exceptiontable parameter.

PyCodeObject *PyCode_NewWithPosOnlyArgs(int argcount, int posonlyargcount, int kwonlyargcount, int nlocals, int stacksize, int flags, PyObject *code, PyObject *consts, PyObject *names, PyObject *varnames, PyObject *freevars, PyObject *cellvars, PyObject *filename, PyObject *name, int firstlineno, PyObject *linetable, PyObject *exceptiontable)

Return value: New reference.

Similar to PyCode_New(), but with an extra “posonlyargcount” for positional-only arguments. The same caveats that apply to PyCode_New also apply to this function.

New in version 3.8.

Changed in version 3.11: Added exceptiontable parameter.

PyCodeObject *PyCode_NewEmpty(const char *filename, const char *funcname, int firstlineno)

Return value: New reference.

Return a new empty code object with the specified filename, function name, and first line number. The resulting code object will raise an Exception if executed.

int PyCode_Addr2Line(PyCodeObject *co, int byte_offset)

Return the line number of the instruction that occurs on or before byte_offset and ends after it. If you just need the line number of a frame, use PyFrame_GetLineNumber() instead.

For efficiently iterating over the line numbers in a code object, use the API described in PEP 626.

int PyCode_Addr2Location(PyObject *co, int byte_offset, int *start_line, int *start_column, int *end_line, int *end_column)

Sets the passed int pointers to the source code line and column numbers for the instruction at byte_offset. Sets the value to 0 when information is not available for any particular element.

Returns 1 if the function succeeds and 0 otherwise.

PyObject *PyCode_GetCode(PyCodeObject *co)

Equivalent to the Python code getattr(co, 'co_code'). Returns a strong reference to a PyBytesObject representing the bytecode in a code object. On error, NULL is returned and an exception is raised.

This PyBytesObject may be created on-demand by the interpreter and does not necessarily represent the bytecode actually executed by CPython. The primary use case for this function is debuggers and profilers.

New in version 3.11.

PyObject *PyCode_GetVarnames(PyCodeObject *co)

Equivalent to the Python code getattr(co, 'co_varnames'). Returns a new reference to a PyTupleObject containing the names of the local variables. On error, NULL is returned and an exception is raised.

New in version 3.11.

PyObject *PyCode_GetCellvars(PyCodeObject *co)

Equivalent to the Python code getattr(co, 'co_cellvars'). Returns a new reference to a PyTupleObject containing the names of the local variables that are referenced by nested functions. On error, NULL is returned and an exception is raised.

New in version 3.11.

PyObject *PyCode_GetFreevars(PyCodeObject *co)

Equivalent to the Python code getattr(co, 'co_freevars'). Returns a new reference to a PyTupleObject containing the names of the free variables. On error, NULL is returned and an exception is raised.

New in version 3.11.

int PyCode_AddWatcher(PyCode_WatchCallback callback)

Register callback as a code object watcher for the current interpreter. Return an ID which may be passed to PyCode_ClearWatcher(). In case of error (e.g. no more watcher IDs available), return -1 and set an exception.

New in version 3.12.

int PyCode_ClearWatcher(int watcher_id)

Clear watcher identified by watcher_id previously returned from PyCode_AddWatcher() for the current interpreter. Return 0 on success, or -1 and set an exception on error (e.g. if the given watcher_id was never registered.)

New in version 3.12.

type PyCodeEvent

Enumeration of possible code object watcher events: - PY_CODE_EVENT_CREATE - PY_CODE_EVENT_DESTROY

New in version 3.12.

typedef int (*PyCode_WatchCallback)(PyCodeEvent event, PyCodeObject *co)

Type of a code object watcher callback function.

If event is PY_CODE_EVENT_CREATE, then the callback is invoked after co has been fully initialized. Otherwise, the callback is invoked before the destruction of co takes place, so the prior state of co can be inspected.

Users of this API should not rely on internal runtime implementation details. Such details may include, but are not limited to, the exact order and timing of creation and destruction of code objects. While changes in these details may result in differences observable by watchers (including whether a callback is invoked or not), it does not change the semantics of the Python code being executed.

If the callback returns with an exception set, it must return -1; this exception will be printed as an unraisable exception using PyErr_WriteUnraisable(). Otherwise it should return 0.

New in version 3.12.