inspect — Inspect live objects¶

Types and members¶

The 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 getmembers(). They also help you determine when you can expect to find the following special attributes (see Import-related attributes on module objects for module attributes):

inspect.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

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 __dir__().

inspect.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

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.

Added in version 3.11.

inspect.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 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.

Changed in version 3.3: The function is based directly on importlib.

inspect.ismodule(object)¶

Return True if the object is a module.

inspect.isclass(object)¶

Return True if the object is a class, whether built-in or created in Python code.

inspect.ismethod(object)¶

Return True if the object is a bound method written in Python.

inspect.isfunction(object)¶

Return True if the object is a Python function, which includes functions created by a lambda expression.

inspect.isgeneratorfunction(object)¶

Return True if the object is a Python generator function.

Changed in version 3.8: Functions wrapped in functools.partial() now return True if the wrapped function is a Python generator function.

Changed in version 3.13: Functions wrapped in functools.partialmethod() now return True if the wrapped function is a Python generator function.

inspect.isgenerator(object)¶

Return True if the object is a generator.

inspect.iscoroutinefunction(object)¶

Return True if the object is a coroutine function (a function defined with an async def syntax), a functools.partial() wrapping a coroutine function, or a sync function marked with markcoroutinefunction().

Added in version 3.5.

Changed in version 3.8: Functions wrapped in functools.partial() now return True if the wrapped function is a coroutine function.

Changed in version 3.12: Sync functions marked with markcoroutinefunction() now return True.

Changed in version 3.13: Functions wrapped in functools.partialmethod() now return True if the wrapped function is a coroutine function.

inspect.markcoroutinefunction(func)¶

Decorator to mark a callable as a coroutine function if it would not otherwise be detected by iscoroutinefunction().

This may be of use for sync functions that return a coroutine, if the function is passed to an API that requires iscoroutinefunction().

When possible, using an async def function is preferred. Also acceptable is calling the function and testing the return with iscoroutine().

Added in version 3.12.

inspect.iscoroutine(object)¶

Return True if the object is a coroutine created by an async def function.

Added in version 3.5.

inspect.isawaitable(object)¶

Return True if the object can be used in await expression.

Can also be used to distinguish generator-based coroutines from regular generators:

import types

def gen():
    yield
@types.coroutine
def gen_coro():
    yield

assert not isawaitable(gen())
assert isawaitable(gen_coro())

Added in version 3.5.

inspect.isasyncgenfunction(object)¶

Return True if the object is an asynchronous generator function, for example:

>>> async def agen():
...     yield 1
...
>>> inspect.isasyncgenfunction(agen)
True

Added in version 3.6.

Changed in version 3.8: Functions wrapped in functools.partial() now return True if the wrapped function is an asynchronous generator function.

Changed in version 3.13: Functions wrapped in functools.partialmethod() now return True if the wrapped function is a coroutine function.

inspect.isasyncgen(object)¶

Return True if the object is an asynchronous generator iterator created by an asynchronous generator function.

Added in version 3.6.

inspect.istraceback(object)¶

Return True if the object is a traceback.

inspect.isframe(object)¶

Return True if the object is a frame.

inspect.iscode(object)¶

Return True if the object is a code.

inspect.isbuiltin(object)¶

Return True if the object is a built-in function or a bound built-in method.

inspect.ismethodwrapper(object)¶

Return True if the type of object is a MethodWrapperType.

These are instances of MethodWrapperType, such as __str__(), __eq__() and __repr__().

Added in version 3.11.

inspect.isroutine(object)¶

Return True if the object is a user-defined or built-in function or method.

inspect.isabstract(object)¶

Return True if the object is an abstract base class.

inspect.ismethoddescriptor(object)¶

Return True if the object is a method descriptor, but not if ismethod(), isclass(), isfunction() or isbuiltin() are true.

This, for example, is true of int.__add__. An object passing this test has a __get__() method, but not a __set__() method or a __delete__() method. Beyond that, the set of attributes varies. A __name__ attribute is usually sensible, and __doc__ often is.

Methods implemented via descriptors that also pass one of the other tests return False from the ismethoddescriptor() test, simply because the other tests promise more – you can, e.g., count on having the __func__ attribute (etc) when an object passes ismethod().

Changed in version 3.13: This function no longer incorrectly reports objects with __get__() and __delete__(), but not __set__(), as being method descriptors (such objects are data descriptors, not method descriptors).

inspect.isdatadescriptor(object)¶

Return True if the object is a data descriptor.

Data descriptors have a __set__ or a __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 __name__ and __doc__ attributes (properties, getsets, and members have both of these attributes), but this is not guaranteed.

inspect.isgetsetdescriptor(object)¶

Return True if the object is a getset descriptor.

CPython implementation detail: getsets are attributes defined in extension modules via PyGetSetDef structures. For Python implementations without such types, this method will always return False.

inspect.ismemberdescriptor(object)¶

Return True if the object is a member descriptor.

CPython implementation detail: Member descriptors are attributes defined in extension modules via PyMemberDef structures. For Python implementations without such types, this method will always return False.

Retrieving source code¶

inspect.getdoc(object)¶

Get the documentation string for an object, cleaned up with 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.

Changed in version 3.5: Documentation strings are now inherited if not overridden.

inspect.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.

inspect.getfile(object)¶

Return the name of the (text or binary) file in which an object was defined. This will fail with a TypeError if the object is a built-in module, class, or function.

inspect.getmodule(object)¶

Try to guess which module an object was defined in. Return None if the module cannot be determined.

inspect.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 TypeError if the object is a built-in module, class, or function.

inspect.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 OSError is raised if the source code cannot be retrieved. A TypeError is raised if the object is a built-in module, class, or function.

Changed in version 3.3: OSError is raised instead of IOError, now an alias of the former.

inspect.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 OSError is raised if the source code cannot be retrieved. A TypeError is raised if the object is a built-in module, class, or function.

Changed in version 3.3: OSError is raised instead of IOError, now an alias of the former.

inspect.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.

Introspecting callables with the Signature object¶

The Signature object represents the call signature of a callable object and its return annotation. To retrieve a Signature object, use the signature() function.

inspect.signature(callable, *, follow_wrapped=True, globals=None, locals=None, eval_str=False)¶

Return a 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 functools.partial() objects.

For objects defined in modules using stringized annotations (from __future__ import annotations), signature() will attempt to automatically un-stringize the annotations using get_annotations(). The globals, locals, and eval_str parameters are passed into get_annotations() when resolving the annotations; see the documentation for get_annotations() for instructions on how to use these parameters.

Raises ValueError if no signature can be provided, and 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 in get_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 the FAQ entry on positional-only parameters.

Changed in version 3.5: The follow_wrapped parameter was added. Pass False to get a signature of callable specifically (callable.__wrapped__ will not be used to unwrap decorated callables.)

Changed in version 3.10: The globals, locals, and eval_str parameters were added.

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.

CPython implementation detail: If the passed object has a __signature__ attribute, we may use it to create the signature. The exact semantics are an implementation detail and are subject to unannounced changes. Consult the source code for current semantics.

class inspect.Signature(parameters=None, *, return_annotation=Signature.empty)¶

A Signature object represents the call signature of a function and its return annotation. For each parameter accepted by the function it stores a Parameter object in its parameters collection.

The optional parameters argument is a sequence of Parameter objects, which is validated to check that there are no parameters with duplicate names, and that the parameters are in the right order, i.e. positional-only first, then positional-or-keyword, and that parameters with defaults follow parameters without defaults.

The optional return_annotation argument can be an arbitrary Python object. It represents the “return” annotation of the callable.

Signature objects are immutable. Use Signature.replace() or copy.replace() to make a modified copy.

Changed in version 3.5: Signature objects are now picklable and hashable.

empty¶

A special class-level marker to specify absence of a return annotation.

parameters¶

An ordered mapping of parameters’ names to the corresponding Parameter objects. Parameters appear in strict definition order, including keyword-only parameters.

Changed in version 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.

return_annotation¶

The “return” annotation for the callable. If the callable has no “return” annotation, this attribute is set to Signature.empty.

bind(*args, **kwargs)¶

Create a mapping from positional and keyword arguments to parameters. Returns BoundArguments if *args and **kwargs match the signature, or raises a TypeError.

bind_partial(*args, **kwargs)¶

Works the same way as Signature.bind(), but allows the omission of some required arguments (mimics functools.partial() behavior.) Returns BoundArguments, or raises a TypeError if the passed arguments do not match the signature.

replace(*[, parameters][, return_annotation])¶

Create a new Signature instance based on the instance replace() was invoked on. It is possible to pass different parameters and/or return_annotation to override the corresponding properties of the base signature. To remove return_annotation from the copied Signature, pass in Signature.empty.

>>> def test(a, b):
...     pass
...
>>> sig = signature(test)
>>> new_sig = sig.replace(return_annotation="new return anno")
>>> str(new_sig)
"(a, b) -> 'new return anno'"

Signature objects are also supported by the generic function copy.replace().

format(*, max_width=None)¶

Create a string representation of the Signature object.

If max_width is passed, the method will attempt to fit the signature into lines of at most max_width characters. If the signature is longer than max_width, all parameters will be on separate lines.

Added in version 3.13.

classmethod from_callable(obj, *, follow_wrapped=True, globals=None, locals=None, eval_str=False)¶

Return a Signature (or its subclass) object for a given callable obj.

This method simplifies subclassing of Signature:

class MySignature(Signature):
    pass
sig = MySignature.from_callable(sum)
assert isinstance(sig, MySignature)

Its behavior is otherwise identical to that of signature().

Added in version 3.5.

Changed in version 3.10: The globals, locals, and eval_str parameters were added.

class inspect.Parameter(name, kind, *, default=Parameter.empty, annotation=Parameter.empty)¶

Parameter objects are immutable. Instead of modifying a Parameter object, you can use Parameter.replace() or copy.replace() to create a modified copy.

Changed in version 3.5: Parameter objects are now picklable and hashable.

empty¶

A special class-level marker to specify absence of default values and annotations.

name¶

The name of the parameter as a string. The name must be a valid Python identifier.

CPython implementation detail: CPython generates implicit parameter names of the form .0 on the code objects used to implement comprehensions and generator expressions.

Changed in version 3.6: These parameter names are now exposed by this module as names like implicit0.

default¶

The default value for the parameter. If the parameter has no default value, this attribute is set to Parameter.empty.

annotation¶

The annotation for the parameter. If the parameter has no annotation, this attribute is set to Parameter.empty.

kind¶

Describes how argument values are bound to the parameter. The possible values are accessible via Parameter (like Parameter.KEYWORD_ONLY), and support comparison and ordering, in the following order:

Name	Meaning
POSITIONAL_ONLY	Value must be supplied as a positional argument. Positional only parameters are those which appear before a / entry (if present) in a Python function definition.
POSITIONAL_OR_KEYWORD	Value may be supplied as either a keyword or positional argument (this is the standard binding behaviour for functions implemented in Python.)
VAR_POSITIONAL	A tuple of positional arguments that aren’t bound to any other parameter. This corresponds to a *args parameter in a Python function definition.
KEYWORD_ONLY	Value must be supplied as a keyword argument. Keyword only parameters are those which appear after a * or *args entry in a Python function definition.
VAR_KEYWORD	A dict of keyword arguments that aren’t bound to any other parameter. This corresponds to a **kwargs parameter in a Python function definition.

Example: print all keyword-only arguments without default values:

>>> def foo(a, b, *, c, d=10):
...     pass

>>> sig = signature(foo)
>>> for param in sig.parameters.values():
...     if (param.kind == param.KEYWORD_ONLY and
...                        param.default is param.empty):
...         print('Parameter:', param)
Parameter: c

kind.description¶

Describes an enum value of Parameter.kind.

Added in version 3.8.

Example: print all descriptions of arguments:

>>> def foo(a, b, *, c, d=10):
...     pass

>>> sig = signature(foo)
>>> for param in sig.parameters.values():
...     print(param.kind.description)
positional or keyword
positional or keyword
keyword-only
keyword-only

replace(*[, name][, kind][, default][, annotation])¶

Create a new Parameter instance based on the instance replaced was invoked on. To override a Parameter attribute, pass the corresponding argument. To remove a default value or/and an annotation from a Parameter, pass Parameter.empty.

>>> from inspect import Parameter
>>> param = Parameter('foo', Parameter.KEYWORD_ONLY, default=42)
>>> str(param)
'foo=42'

>>> str(param.replace()) # Will create a shallow copy of 'param'
'foo=42'

>>> str(param.replace(default=Parameter.empty, annotation='spam'))
"foo: 'spam'"

Parameter objects are also supported by the generic function copy.replace().

Changed in version 3.4: In Python 3.3 Parameter objects were allowed to have name set to None if their kind was set to POSITIONAL_ONLY. This is no longer permitted.

class inspect.BoundArguments¶

Result of a Signature.bind() or Signature.bind_partial() call. Holds the mapping of arguments to the function’s parameters.

arguments¶

A mutable mapping of parameters’ names to arguments’ values. Contains only explicitly bound arguments. Changes in arguments will reflect in args and kwargs.

Should be used in conjunction with Signature.parameters for any argument processing purposes.

Note

Arguments for which Signature.bind() or Signature.bind_partial() relied on a default value are skipped. However, if needed, use BoundArguments.apply_defaults() to add them.

Changed in version 3.9: arguments is now of type dict. Formerly, it was of type collections.OrderedDict.

args¶

A tuple of positional arguments values. Dynamically computed from the arguments attribute.

kwargs¶

A dict of keyword arguments values. Dynamically computed from the arguments attribute. Arguments that can be passed positionally are included in args instead.

signature¶

A reference to the parent Signature object.

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': ()}

Added in version 3.5.

The args and 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)

Classes and functions¶

inspect.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.

inspect.getfullargspec(func)¶

Get the names and default values of a Python function’s parameters. A 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 signature() and 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.

Changed in version 3.4: This function is now based on