:mod:`inspect` --- Inspect live objects
.. module:: inspect :synopsis: Extract information and source code from live objects.
.. moduleauthor:: Ka-Ping Yee <ping@lfw.org>
.. sectionauthor:: Ka-Ping Yee <ping@lfw.org>
Source code: :source:`Lib/inspect.py`
The :mod:`inspect` module provides several useful functions to help get information about live objects such as modules, classes, methods, functions, tracebacks, frame objects, and code objects. For example, it can help you examine the contents of a class, retrieve the source code of a method, extract and format the argument list for a function, or get all the information you need to display a detailed traceback.
There are four main kinds of services provided by this module: type checking, getting source code, inspecting classes and functions, and examining the interpreter stack.
The :func:`getmembers` function retrieves the members of an object such as a class or module. The functions whose names begin with "is" are mainly provided as convenient choices for the second argument to :func:`getmembers`. They also help you determine when you can expect to find the following special attributes (see :ref:`import-mod-attrs` for module attributes):
| Type | Attribute | Description |
|---|---|---|
| class | __doc__ | documentation string |
| __name__ | name with which this class was defined | |
| __qualname__ | qualified name | |
| __module__ | name of module in which this class was defined | |
| method | __doc__ | documentation string |
| __name__ | name with which this method was defined | |
| __qualname__ | qualified name | |
| __func__ | function object containing implementation of method | |
| __self__ | instance to which this
method is bound, or
None |
|
| __module__ | name of module in which this method was defined | |
| function | __doc__ | documentation string |
| __name__ | name with which this function was defined | |
| __qualname__ | qualified name | |
| __code__ | code object containing compiled function :term:`bytecode` | |
| __defaults__ | tuple of any default values for positional or keyword parameters | |
| __kwdefaults__ | mapping of any default values for keyword-only parameters | |
| __globals__ | global namespace in which this function was defined | |
| __builtins__ | builtins namespace | |
| __annotations__ | mapping of parameters
names to annotations;
"return" key is
reserved for return
annotations. |
|
| __module__ | name of module in which this function was defined | |
| traceback | tb_frame | frame object at this level |
| tb_lasti | index of last attempted instruction in bytecode | |
| tb_lineno | current line number in Python source code | |
| tb_next | next inner traceback object (called by this level) | |
| frame | f_back | next outer frame object (this frame's caller) |
| f_builtins | builtins namespace seen by this frame | |
| f_code | code object being executed in this frame | |
| f_globals | global namespace seen by this frame | |
| f_lasti | index of last attempted instruction in bytecode | |
| f_lineno | current line number in Python source code | |
| f_locals | local namespace seen by this frame | |
| f_trace | tracing function for this
frame, or None |
|
| code | co_argcount | number of arguments (not including keyword only arguments, * or ** args) |
| co_code | string of raw compiled bytecode | |
| co_cellvars | tuple of names of cell variables (referenced by containing scopes) | |
| co_consts | tuple of constants used in the bytecode | |
| co_filename | name of file in which this code object was created | |
| co_firstlineno | number of first line in Python source code | |
| co_flags | bitmap of CO_* flags,
read more :ref:`here
<inspect-module-co-flags>` |
|
| co_lnotab | encoded mapping of line numbers to bytecode indices | |
| co_freevars | tuple of names of free variables (referenced via a function's closure) | |
| co_posonlyargcount | number of positional only arguments | |
| co_kwonlyargcount | number of keyword only arguments (not including ** arg) | |
| co_name | name with which this code object was defined | |
| co_qualname | fully qualified name with which this code object was defined | |
| co_names | tuple of names other than arguments and function locals | |
| co_nlocals | number of local variables | |
| co_stacksize | virtual machine stack space required | |
| co_varnames | tuple of names of arguments and local variables | |
| generator | __name__ | name |
| __qualname__ | qualified name | |
| gi_frame | frame | |
| gi_running | is the generator running? | |
| gi_code | code | |
| gi_yieldfrom | object being iterated by
yield from, or
None |
|
| coroutine | __name__ | name |
| __qualname__ | qualified name | |
| cr_await | object being awaited on,
or None |
|
| cr_frame | frame | |
| cr_running | is the coroutine running? | |
| cr_code | code | |
| cr_origin | where coroutine was
created, or None. See
|coroutine-origin-link| |
|
| builtin | __doc__ | documentation string |
| __name__ | original name of this function or method | |
| __qualname__ | qualified name | |
| __self__ | instance to which a
method is bound, or
None |
.. versionchanged:: 3.5 Add ``__qualname__`` and ``gi_yieldfrom`` attributes to generators. The ``__name__`` attribute of generators is now set from the function name, instead of the code name, and it can now be modified.
.. versionchanged:: 3.7 Add ``cr_origin`` attribute to coroutines.
.. versionchanged:: 3.10 Add ``__builtins__`` attribute to functions.
.. function:: getmembers(object[, predicate])
Return all the members of an object in a list of ``(name, value)``
pairs sorted by name. If the optional *predicate* argument—which will be
called with the ``value`` object of each member—is supplied, only members
for which the predicate returns a true value are included.
.. note::
:func:`getmembers` will only return class attributes defined in the
metaclass when the argument is a class and those attributes have been
listed in the metaclass' custom :meth:`__dir__`.
.. function:: getmembers_static(object[, predicate])
Return all the members of an object in a list of ``(name, value)``
pairs sorted by name without triggering dynamic lookup via the descriptor
protocol, __getattr__ or __getattribute__. Optionally, only return members
that satisfy a given predicate.
.. note::
:func:`getmembers_static` may not be able to retrieve all members
that getmembers can fetch (like dynamically created attributes)
and may find members that getmembers can't (like descriptors
that raise AttributeError). It can also return descriptor objects
instead of instance members in some cases.
.. versionadded:: 3.11
.. function:: getmodulename(path)
Return the name of the module named by the file *path*, without including the
names of enclosing packages. The file extension is checked against all of
the entries in :func:`importlib.machinery.all_suffixes`. If it matches,
the final path component is returned with the extension removed.
Otherwise, ``None`` is returned.
Note that this function *only* returns a meaningful name for actual
Python modules - paths that potentially refer to Python packages will
still return ``None``.
.. versionchanged:: 3.3
The function is based directly on :mod:`importlib`.
.. function:: ismodule(object) Return ``True`` if the object is a module.
.. function:: isclass(object) Return ``True`` if the object is a class, whether built-in or created in Python code.
.. function:: ismethod(object) Return ``True`` if the object is a bound method written in Python.
.. function:: isfunction(object) Return ``True`` if the object is a Python function, which includes functions created by a :term:`lambda` expression.
.. function:: isgeneratorfunction(object)
Return ``True`` if the object is a Python generator function.
.. versionchanged:: 3.8
Functions wrapped in :func:`functools.partial` now return ``True`` if the
wrapped function is a Python generator function.
.. function:: isgenerator(object) Return ``True`` if the object is a generator.
.. function:: iscoroutinefunction(object)
Return ``True`` if the object is a :term:`coroutine function` (a function
defined with an :keyword:`async def` syntax), a :func:`functools.partial`
wrapping a :term:`coroutine function`, or a sync function marked with
:func:`markcoroutinefunction`.
.. versionadded:: 3.5
.. versionchanged:: 3.8
Functions wrapped in :func:`functools.partial` now return ``True`` if the
wrapped function is a :term:`coroutine function`.
.. versionchanged:: 3.12
Sync functions marked with :func:`markcoroutinefunction` now return
``True``.
.. function:: markcoroutinefunction(func) Decorator to mark a callable as a :term:`coroutine function` if it would not otherwise be detected by :func:`iscoroutinefunction`. This may be of use for sync functions that return a :term:`coroutine`, if the function is passed to an API that requires :func:`iscoroutinefunction`. When possible, using an :keyword:`async def` function is preferred. Also acceptable is calling the function and testing the return with :func:`iscoroutine`. .. versionadded:: 3.12
.. function:: iscoroutine(object) Return ``True`` if the object is a :term:`coroutine` created by an :keyword:`async def` function. .. versionadded:: 3.5
.. function:: isawaitable(object)
Return ``True`` if the object can be used in :keyword:`await` expression.
Can also be used to distinguish generator-based coroutines from regular
generators::
def gen():
yield
@types.coroutine
def gen_coro():
yield
assert not isawaitable(gen())
assert isawaitable(gen_coro())
.. versionadded:: 3.5
.. function:: isasyncgenfunction(object)
Return ``True`` if the object is an :term:`asynchronous generator` function,
for example::
>>> async def agen():
... yield 1
...
>>> inspect.isasyncgenfunction(agen)
True
.. versionadded:: 3.6
.. versionchanged:: 3.8
Functions wrapped in :func:`functools.partial` now return ``True`` if the
wrapped function is a :term:`asynchronous generator` function.
.. function:: isasyncgen(object) Return ``True`` if the object is an :term:`asynchronous generator iterator` created by an :term:`asynchronous generator` function. .. versionadded:: 3.6
.. function:: istraceback(object) Return ``True`` if the object is a traceback.
.. function:: isframe(object) Return ``True`` if the object is a frame.
.. function:: iscode(object) Return ``True`` if the object is a code.
.. function:: isbuiltin(object) Return ``True`` if the object is a built-in function or a bound built-in method.
.. function:: ismethodwrapper(object) Return ``True`` if the type of object is a :class:`~types.MethodWrapperType`. These are instances of :class:`~types.MethodWrapperType`, such as :meth:`~object.__str__`, :meth:`~object.__eq__` and :meth:`~object.__repr__`. .. versionadded:: 3.11
.. function:: isroutine(object) Return ``True`` if the object is a user-defined or built-in function or method.
.. function:: isabstract(object) Return ``True`` if the object is an abstract base class.
.. function:: ismethoddescriptor(object) Return ``True`` if the object is a method descriptor, but not if :func:`ismethod`, :func:`isclass`, :func:`isfunction` or :func:`isbuiltin` are true. This, for example, is true of ``int.__add__``. An object passing this test has a :meth:`~object.__get__` method but not a :meth:`~object.__set__` method, but beyond that the set of attributes varies. A :attr:`~definition.__name__` attribute is usually sensible, and :attr:`__doc__` often is. Methods implemented via descriptors that also pass one of the other tests return ``False`` from the :func:`ismethoddescriptor` test, simply because the other tests promise more -- you can, e.g., count on having the :attr:`__func__` attribute (etc) when an object passes :func:`ismethod`.
.. function:: isdatadescriptor(object) Return ``True`` if the object is a data descriptor. Data descriptors have a :attr:`~object.__set__` or a :attr:`~object.__delete__` method. Examples are properties (defined in Python), getsets, and members. The latter two are defined in C and there are more specific tests available for those types, which is robust across Python implementations. Typically, data descriptors will also have :attr:`~definition.__name__` and :attr:`__doc__` attributes (properties, getsets, and members have both of these attributes), but this is not guaranteed.
.. function:: isgetsetdescriptor(object)
Return ``True`` if the object is a getset descriptor.
.. impl-detail::
getsets are attributes defined in extension modules via
:c:type:`PyGetSetDef` structures. For Python implementations without such
types, this method will always return ``False``.
.. function:: ismemberdescriptor(object)
Return ``True`` if the object is a member descriptor.
.. impl-detail::
Member descriptors are attributes defined in extension modules via
:c:type:`PyMemberDef` structures. For Python implementations without such
types, this method will always return ``False``.
.. function:: getdoc(object)
Get the documentation string for an object, cleaned up with :func:`cleandoc`.
If the documentation string for an object is not provided and the object is
a class, a method, a property or a descriptor, retrieve the documentation
string from the inheritance hierarchy.
Return ``None`` if the documentation string is invalid or missing.
.. versionchanged:: 3.5
Documentation strings are now inherited if not overridden.
.. function:: getcomments(object) Return in a single string any lines of comments immediately preceding the object's source code (for a class, function, or method), or at the top of the Python source file (if the object is a module). If the object's source code is unavailable, return ``None``. This could happen if the object has been defined in C or the interactive shell.
.. function:: getfile(object) Return the name of the (text or binary) file in which an object was defined. This will fail with a :exc:`TypeError` if the object is a built-in module, class, or function.
.. function:: getmodule(object) Try to guess which module an object was defined in. Return ``None`` if the module cannot be determined.
.. function:: getsourcefile(object) Return the name of the Python source file in which an object was defined or ``None`` if no way can be identified to get the source. This will fail with a :exc:`TypeError` if the object is a built-in module, class, or function.
.. function:: getsourcelines(object)
Return a list of source lines and starting line number for an object. The
argument may be a module, class, method, function, traceback, frame, or code
object. The source code is returned as a list of the lines corresponding to the
object and the line number indicates where in the original source file the first
line of code was found. An :exc:`OSError` is raised if the source code cannot
be retrieved.
.. versionchanged:: 3.3
:exc:`OSError` is raised instead of :exc:`IOError`, now an alias of the
former.
.. function:: getsource(object)
Return the text of the source code for an object. The argument may be a module,
class, method, function, traceback, frame, or code object. The source code is
returned as a single string. An :exc:`OSError` is raised if the source code
cannot be retrieved.
.. versionchanged:: 3.3
:exc:`OSError` is raised instead of :exc:`IOError`, now an alias of the
former.
.. function:: cleandoc(doc) Clean up indentation from docstrings that are indented to line up with blocks of code. All leading whitespace is removed from the first line. Any leading whitespace that can be uniformly removed from the second line onwards is removed. Empty lines at the beginning and end are subsequently removed. Also, all tabs are expanded to spaces.
.. versionadded:: 3.3
The Signature object represents the call signature of a callable object and its return annotation. To retrieve a Signature object, use the :func:`signature` function.
.. function:: signature(callable, *, follow_wrapped=True, globals=None, locals=None, eval_str=False)
Return a :class:`Signature` object for the given ``callable``::
>>> from inspect import signature
>>> def foo(a, *, b:int, **kwargs):
... pass
>>> sig = signature(foo)
>>> str(sig)
'(a, *, b:int, **kwargs)'
>>> str(sig.parameters['b'])
'b:int'
>>> sig.parameters['b'].annotation
<class 'int'>
Accepts a wide range of Python callables, from plain functions and classes to
:func:`functools.partial` objects.
For objects defined in modules using stringized annotations
(``from __future__ import annotations``), :func:`signature` will
attempt to automatically un-stringize the annotations using
:func:`inspect.get_annotations()`. The
``global``, ``locals``, and ``eval_str`` parameters are passed
into :func:`inspect.get_annotations()` when resolving the
annotations; see the documentation for :func:`inspect.get_annotations()`
for instructions on how to use these parameters.
Raises :exc:`ValueError` if no signature can be provided, and
:exc:`TypeError` if that type of object is not supported. Also,
if the annotations are stringized, and ``eval_str`` is not false,
the ``eval()`` call(s) to un-stringize the annotations could
potentially raise any kind of exception.
A slash(/) in the signature of a function denotes that the parameters prior
to it are positional-only. For more info, see
:ref:`the FAQ entry on positional-only parameters <faq-positional-only-arguments>`.
.. versionadded:: 3.5
``follow_wrapped`` parameter. Pass ``False`` to get a signature of
``callable`` specifically (``callable.__wrapped__`` will not be used to
unwrap decorated callables.)
.. versionadded:: 3.10
``globals``, ``locals``, and ``eval_str`` parameters.
.. note::
Some callables may not be introspectable in certain implementations of
Python. For example, in CPython, some built-in functions defined in
C provide no metadata about their arguments.
Result of a :meth:`Signature.bind` or :meth:`Signature.bind_partial` call. Holds the mapping of arguments to the function's parameters.
.. attribute:: BoundArguments.arguments
A mutable mapping of parameters' names to arguments' values.
Contains only explicitly bound arguments. Changes in :attr:`arguments`
will reflect in :attr:`args` and :attr:`kwargs`.
Should be used in conjunction with :attr:`Signature.parameters` for any
argument processing purposes.
.. note::
Arguments for which :meth:`Signature.bind` or
:meth:`Signature.bind_partial` relied on a default value are skipped.
However, if needed, use :meth:`BoundArguments.apply_defaults` to add
them.
.. versionchanged:: 3.9
:attr:`arguments` is now of type :class:`dict`. Formerly, it was of
type :class:`collections.OrderedDict`.
.. attribute:: BoundArguments.args A tuple of positional arguments values. Dynamically computed from the :attr:`arguments` attribute.
.. attribute:: BoundArguments.kwargs A dict of keyword arguments values. Dynamically computed from the :attr:`arguments` attribute.
.. attribute:: BoundArguments.signature A reference to the parent :class:`Signature` object.
.. method:: BoundArguments.apply_defaults()
Set default values for missing arguments.
For variable-positional arguments (``*args``) the default is an
empty tuple.
For variable-keyword arguments (``**kwargs``) the default is an
empty dict.
::
>>> def foo(a, b='ham', *args): pass
>>> ba = inspect.signature(foo).bind('spam')
>>> ba.apply_defaults()
>>> ba.arguments
{'a': 'spam', 'b': 'ham', 'args': ()}
.. versionadded:: 3.5
The :attr:`args` and :attr:`kwargs` properties can be used to invoke functions:
def test(a, *, b):
...
sig = signature(test)
ba = sig.bind(10, b=20)
test(*ba.args, **ba.kwargs)
.. seealso::
:pep:`362` - Function Signature Object.
The detailed specification, implementation details and examples.
.. function:: getclasstree(classes, unique=False) Arrange the given list of classes into a hierarchy of nested lists. Where a nested list appears, it contains classes derived from the class whose entry immediately precedes the list. Each entry is a 2-tuple containing a class and a tuple of its base classes. If the *unique* argument is true, exactly one entry appears in the returned structure for each class in the given list. Otherwise, classes using multiple inheritance and their descendants will appear multiple times.
.. function:: getfullargspec(func)
Get the names and default values of a Python function's parameters. A
:term:`named tuple` is returned:
``FullArgSpec(args, varargs, varkw, defaults, kwonlyargs, kwonlydefaults,
annotations)``
*args* is a list of the positional parameter names.
*varargs* is the name of the ``*`` parameter or ``None`` if arbitrary
positional arguments are not accepted.
*varkw* is the name of the ``**`` parameter or ``None`` if arbitrary
keyword arguments are not accepted.
*defaults* is an *n*-tuple of default argument values corresponding to the
last *n* positional parameters, or ``None`` if there are no such defaults
defined.
*kwonlyargs* is a list of keyword-only parameter names in declaration order.
*kwonlydefaults* is a dictionary mapping parameter names from *kwonlyargs*
to the default values used if no argument is supplied.
*annotations* is a dictionary mapping parameter names to annotations.
The special key ``"return"`` is used to report the function return value
annotation (if any).
Note that :func:`signature` and
:ref:`Signature Object <inspect-signature-object>` provide the recommended
API for callable introspection, and support additional behaviours (like
positional-only arguments) that are sometimes encountered in extension module
APIs. This function is retained primarily for use in code that needs to
maintain compatibility with the Python 2 ``inspect`` module API.
.. versionchanged:: 3.4
This function is now based on :func:`signature`, but still ignores
``__wrapped__`` attributes and includes the already bound first
parameter in the signature output for bound methods.
.. versionchanged:: 3.6
This method was previously documented as deprecated in favour of
:func:`signature` in Python 3.5, but that decision has been reversed
in order to restore a clearly supported standard interface for
single-source Python 2/3 code migrating away from the legacy
:func:`getargspec` API.
.. versionchanged:: 3.7
Python only explicitly guaranteed that it preserved the declaration
order of keyword-only parameters as of version 3.7, although in practice
this order had always been preserved in Python 3.
.. function:: getargvalues(frame)
Get information about arguments passed into a particular frame. A
:term:`named tuple` ``ArgInfo(args, varargs, keywords, locals)`` is
returned. *args* is a list of the argument names. *varargs* and *keywords*
are the names of the ``*`` and ``**`` arguments or ``None``. *locals* is the
locals dictionary of the given frame.
.. note::
This function was inadvertently marked as deprecated in Python 3.5.
.. function:: formatargvalues(args[, varargs, varkw, locals, formatarg, formatvarargs, formatvarkw, formatvalue])
Format a pretty argument spec from the four values returned by
:func:`getargvalues`. The format\* arguments are the corresponding optional
formatting functions that are called to turn names and values into strings.
.. note::
This function was inadvertently marked as deprecated in Python 3.5.
.. function:: getmro(cls) Return a tuple of class cls's base classes, including cls, in method resolution order. No class appears more than once in this tuple. Note that the method resolution order depends on cls's type. Unless a very peculiar user-defined metatype is in use, cls will be the first element of the tuple.
.. function:: getcallargs(func, /, *args, **kwds)
Bind the *args* and *kwds* to the argument names of the Python function or
method *func*, as if it was called with them. For bound methods, bind also the
first argument (typically named ``self``) to the associated instance. A dict
is returned, mapping the argument names (including the names of the ``*`` and
``**`` arguments, if any) to their values from *args* and *kwds*. In case of
invoking *func* incorrectly, i.e. whenever ``func(*args, **kwds)`` would raise
an exception because of incompatible signature, an exception of the same type
and the same or similar message is raised. For example::
>>> from inspect import getcallargs
>>> def f(a, b=1, *pos, **named):
... pass
>>> getcallargs(f, 1, 2, 3) == {'a': 1, 'named': {}, 'b': 2, 'pos': (3,)}
True
>>> getcallargs(f, a=2, x=4) == {'a': 2, 'named': {'x': 4}, 'b': 1, 'pos': ()}
True
>>> getcallargs(f)
Traceback (most recent call last):
...
TypeError: f() missing 1 required positional argument: 'a'
.. versionadded:: 3.2
.. deprecated:: 3.5
Use :meth:`Signature.bind` and :meth:`Signature.bind_partial` instead.
.. function:: getclosurevars(func) Get the mapping of external name references in a Python function or method *func* to their current values. A :term:`named tuple` ``ClosureVars(nonlocals, globals, builtins, unbound)`` is returned. *nonlocals* maps referenced names to lexical closure variables, *globals* to the function's module globals and *builtins* to the builtins visible from the function body. *unbound* is the set of names referenced in the function that could not be resolved at all given the current module globals and builtins. :exc:`TypeError` is raised if *func* is not a Python function or method. .. versionadded:: 3.3
.. function:: unwrap(func, *, stop=None) Get the object wrapped by *func*. It follows the chain of :attr:`__wrapped__` attributes returning the last object in the chain. *stop* is an optional callback accepting an object in the wrapper chain as its sole argument that allows the unwrapping to be terminated early if the callback returns a true value. If the callback never returns a true value, the last object in the chain is returned as usual. For example, :func:`signature` uses this to stop unwrapping if any object in the chain has a ``__signature__`` attribute defined. :exc:`ValueError` is raised if a cycle is encountered. .. versionadded:: 3.4
.. function:: get_annotations(obj, *, globals=None, locals=None, eval_str=False)
Compute the annotations dict for an object.
``obj`` may be a callable, class, or module.
Passing in an object of any other type raises :exc:`TypeError`.
Returns a dict. ``get_annotations()`` returns a new dict every time
it's called; calling it twice on the same object will return two
different but equivalent dicts.
This function handles several details for you:
* If ``eval_str`` is true, values of type ``str`` will
be un-stringized using :func:`eval()`. This is intended
for use with stringized annotations
(``from __future__ import annotations``).
* If ``obj`` doesn't have an annotations dict, returns an
empty dict. (Functions and methods always have an
annotations dict; classes, modules, and other types of
callables may not.)
* Ignores inherited annotations on classes. If a class
doesn't have its own annotations dict, returns an empty dict.
* All accesses to object members and dict values are done
using ``getattr()`` and ``dict.get()`` for safety.
* Always, always, always returns a freshly created dict.
``eval_str`` controls whether or not values of type ``str`` are replaced
with the result of calling :func:`eval()` on those values:
* If eval_str is true, :func:`eval()` is called on values of type ``str``.
(Note that ``get_annotations`` doesn't catch exceptions; if :func:`eval()`
raises an exception, it will unwind the stack past the ``get_annotations``
call.)
* If eval_str is false (the default), values of type ``str`` are unchanged.
``globals`` and ``locals`` are passed in to :func:`eval()`; see the documentation
for :func:`eval()` for more information. If ``globals`` or ``locals``
is ``None``, this function may replace that value with a context-specific
default, contingent on ``type(obj)``:
* If ``obj`` is a module, ``globals`` defaults to ``obj.__dict__``.
* If ``obj`` is a class, ``globals`` defaults to
``sys.modules[obj.__module__].__dict__`` and ``locals`` defaults
to the ``obj`` class namespace.
* If ``obj`` is a callable, ``globals`` defaults to ``obj.__globals__``,
although if ``obj`` is a wrapped function (using
``functools.update_wrapper()``) it is first unwrapped.
Calling ``get_annotations`` is best practice for accessing the
annotations dict of any object. See :ref:`annotations-howto` for
more information on annotations best practices.
.. versionadded:: 3.10
Some of the following functions return
:class:`FrameInfo` objects. For backwards compatibility these objects allow
tuple-like operations on all attributes except positions. This behavior
is considered deprecated and may be removed in the future.
.. attribute:: frame The :ref:`frame object <frame-objects>` that the record corresponds to.
.. attribute:: filename The file name associated with the code being executed by the frame this record corresponds to.
.. attribute:: lineno The line number of the current line associated with the code being executed by the frame this record corresponds to.
.. attribute:: function The function name that is being executed by the frame this record corresponds to.
.. attribute:: code_context A list of lines of context from the source code that's being executed by the frame this record corresponds to.
.. attribute:: index The index of the current line being executed in the :attr:`code_context` list.
.. attribute:: positions A :class:`dis.Positions` object containing the start line number, end line number, start column offset, and end column offset associated with the instruction being executed by the frame this record corresponds to.
.. versionchanged:: 3.5 Return a :term:`named tuple` instead of a :class:`tuple`.
.. versionchanged:: 3.11 :class:`!FrameInfo` is now a class instance (that is backwards compatible with the previous :term:`named tuple`).
.. attribute:: filename The file name associated with the code being executed by the frame this traceback corresponds to.
.. attribute:: lineno The line number of the current line associated with the code being executed by the frame this traceback corresponds to.
.. attribute:: function The function name that is being executed by the frame this traceback corresponds to.
.. attribute:: code_context A list of lines of context from the source code that's being executed by the frame this traceback corresponds to.
.. attribute:: index The index of the current line being executed in the :attr:`code_context` list.
.. attribute:: positions A :class:`dis.Positions` object containing the start line number, end line number, start column offset, and end column offset associated with the instruction being executed by the frame this traceback corresponds to.
.. versionchanged:: 3.11 :class:`!Traceback` is now a class instance (that is backwards compatible with the previous :term:`named tuple`).
Note
Keeping references to frame objects, as found in the first element of the frame records these functions return, can cause your program to create reference cycles. Once a reference cycle has been created, the lifespan of all objects which can be accessed from the objects which form the cycle can become much longer even if Python's optional cycle detector is enabled. If such cycles must be created, it is important to ensure they are explicitly broken to avoid the delayed destruction of objects and increased memory consumption which occurs.
Though the cycle detector will catch these, destruction of the frames (and local variables) can be made deterministic by removing the cycle in a :keyword:`finally` clause. This is also important if the cycle detector was disabled when Python was compiled or using :func:`gc.disable`. For example:
def handle_stackframe_without_leak():
frame = inspect.currentframe()
try:
# do something with the frame
finally:
del frame
If you want to keep the frame around (for example to print a traceback later), you can also break reference cycles by using the :meth:`frame.clear` method.
The optional context argument supported by most of these functions specifies the number of lines of context to return, which are centered around the current line.
.. function:: getframeinfo(frame, context=1)
Get information about a frame or traceback object. A :class:`Traceback` object
is returned.
.. versionchanged:: 3.11
A :class:`Traceback` object is returned instead of a named tuple.
.. function:: getouterframes(frame, context=1)
Get a list of :class:`FrameInfo` objects for a frame and all outer frames.
These frames represent the calls that lead to the creation of *frame*. The
first entry in the returned list represents *frame*; the last entry
represents the outermost call on *frame*'s stack.
.. versionchanged:: 3.5
A list of :term:`named tuples <named tuple>`
``FrameInfo(frame, filename, lineno, function, code_context, index)``
is returned.
.. versionchanged:: 3.11
A list of :class:`FrameInfo` objects is returned.
.. function:: getinnerframes(traceback, context=1)
Get a list of :class:`FrameInfo` objects for a traceback's frame and all
inner frames. These frames represent calls made as a consequence of *frame*.
The first entry in the list represents *traceback*; the last entry represents
where the exception was raised.
.. versionchanged:: 3.5
A list of :term:`named tuples <named tuple>`
``FrameInfo(frame, filename, lineno, function, code_context, index)``
is returned.
.. versionchanged:: 3.11
A list of :class:`FrameInfo` objects is returned.
.. function:: currentframe()
Return the frame object for the caller's stack frame.
.. impl-detail::
This function relies on Python stack frame support in the interpreter,
which isn't guaranteed to exist in all implementations of Python. If
running in an implementation without Python stack frame support this
function returns ``None``.
.. function:: stack(context=1)
Return a list of :class:`FrameInfo` objects for the caller's stack. The
first entry in the returned list represents the caller; the last entry
represents the outermost call on the stack.
.. versionchanged:: 3.5
A list of :term:`named tuples <named tuple>`
``FrameInfo(frame, filename, lineno, function, code_context, index)``
is returned.
.. versionchanged:: 3.11
A list of :class:`FrameInfo` objects is returned.
.. function:: trace(context=1)
Return a list of :class:`FrameInfo` objects for the stack between the current
frame and the frame in which an exception currently being handled was raised
in. The first entry in the list represents the caller; the last entry
represents where the exception was raised.
.. versionchanged:: 3.5
A list of :term:`named tuples <named tuple>`
``FrameInfo(frame, filename, lineno, function, code_context, index)``
is returned.
.. versionchanged:: 3.11
A list of :class:`FrameInfo` objects is returned.
Both :func:`getattr` and :func:`hasattr` can trigger code execution when fetching or checking for the existence of attributes. Descriptors, like properties, will be invoked and :meth:`__getattr__` and :meth:`__getattribute__` may be called.
For cases where you want passive introspection, like documentation tools, this can be inconvenient. :func:`getattr_static` has the same signature as :func:`getattr` but avoids executing code when it fetches attributes.
.. function:: getattr_static(obj, attr, default=None) Retrieve attributes without triggering dynamic lookup via the descriptor protocol, :meth:`__getattr__` or :meth:`__getattribute__`. Note: this function may not be able to retrieve all attributes that getattr can fetch (like dynamically created attributes) and may find attributes that getattr can't (like descriptors that raise AttributeError). It can also return descriptors objects instead of instance members. If the instance :attr:`~object.__dict__` is shadowed by another member (for example a property) then this function will be unable to find instance members. .. versionadded:: 3.2
:func:`getattr_static` does not resolve descriptors, for example slot descriptors or getset descriptors on objects implemented in C. The descriptor object is returned instead of the underlying attribute.
You can handle these with code like the following. Note that for arbitrary getset descriptors invoking these may trigger code execution:
# example code for resolving the builtin descriptor types
class _foo:
__slots__ = ['foo']
slot_descriptor = type(_foo.foo)
getset_descriptor = type(type(open(__file__)).name)
wrapper_descriptor = type(str.__dict__['__add__'])
descriptor_types = (slot_descriptor, getset_descriptor, wrapper_descriptor)
result = getattr_static(some_object, 'foo')
if type(result) in descriptor_types:
try:
result = result.__get__()
except AttributeError:
# descriptors can raise AttributeError to
# indicate there is no underlying value
# in which case the descriptor itself will
# have to do
pass
When implementing coroutine schedulers and for other advanced uses of generators, it is useful to determine whether a generator is currently executing, is waiting to start or resume or execution, or has already terminated. :func:`getgeneratorstate` allows the current state of a generator to be determined easily.
.. function:: getgeneratorstate(generator)
Get current state of a generator-iterator.
Possible states are:
* GEN_CREATED: Waiting to start execution.
* GEN_RUNNING: Currently being executed by the interpreter.
* GEN_SUSPENDED: Currently suspended at a yield expression.
* GEN_CLOSED: Execution has completed.
.. versionadded:: 3.2
.. function:: getcoroutinestate(coroutine)
Get current state of a coroutine object. The function is intended to be
used with coroutine objects created by :keyword:`async def` functions, but
will accept any coroutine-like object that has ``cr_running`` and
``cr_frame`` attributes.
Possible states are:
* CORO_CREATED: Waiting to start execution.
* CORO_RUNNING: Currently being executed by the interpreter.
* CORO_SUSPENDED: Currently suspended at an await expression.
* CORO_CLOSED: Execution has completed.
.. versionadded:: 3.5
The current internal state of the generator can also be queried. This is mostly useful for testing purposes, to ensure that internal state is being updated as expected:
.. function:: getgeneratorlocals(generator)
Get the mapping of live local variables in *generator* to their current
values. A dictionary is returned that maps from variable names to values.
This is the equivalent of calling :func:`locals` in the body of the
generator, and all the same caveats apply.
If *generator* is a :term:`generator` with no currently associated frame,
then an empty dictionary is returned. :exc:`TypeError` is raised if
*generator* is not a Python generator object.
.. impl-detail::
This function relies on the generator exposing a Python stack frame
for introspection, which isn't guaranteed to be the case in all
implementations of Python. In such cases, this function will always
return an empty dictionary.
.. versionadded:: 3.3
.. function:: getcoroutinelocals(coroutine) This function is analogous to :func:`~inspect.getgeneratorlocals`, but works for coroutine objects created by :keyword:`async def` functions. .. versionadded:: 3.5
Python code objects have a co_flags attribute, which is a bitmap of
the following flags:
.. data:: CO_OPTIMIZED The code object is optimized, using fast locals.
.. data:: CO_NEWLOCALS If set, a new dict will be created for the frame's ``f_locals`` when the code object is executed.
.. data:: CO_VARARGS The code object has a variable positional parameter (``*args``-like).
.. data:: CO_VARKEYWORDS The code object has a variable keyword parameter (``**kwargs``-like).
.. data:: CO_NESTED The flag is set when the code object is a nested function.
.. data:: CO_GENERATOR The flag is set when the code object is a generator function, i.e. a generator object is returned when the code object is executed.
.. data:: CO_COROUTINE The flag is set when the code object is a coroutine function. When the code object is executed it returns a coroutine object. See :pep:`492` for more details. .. versionadded:: 3.5
.. data:: CO_ITERABLE_COROUTINE The flag is used to transform generators into generator-based coroutines. Generator objects with this flag can be used in ``await`` expression, and can ``yield from`` coroutine objects. See :pep:`492` for more details. .. versionadded:: 3.5
.. data:: CO_ASYNC_GENERATOR The flag is set when the code object is an asynchronous generator function. When the code object is executed it returns an asynchronous generator object. See :pep:`525` for more details. .. versionadded:: 3.6
Note
The flags are specific to CPython, and may not be defined in other Python implementations. Furthermore, the flags are an implementation detail, and can be removed or deprecated in future Python releases. It's recommended to use public APIs from the :mod:`inspect` module for any introspection needs.
The :mod:`inspect` module also provides a basic introspection capability from the command line.
.. program:: inspect
By default, accepts the name of a module and prints the source of that module. A class or function within the module can be printed instead by appended a colon and the qualified name of the target object.
.. cmdoption:: --details Print information about the specified object rather than the source code