inspect --- 检查对象

源代码: Lib/inspect.py

---

inspect 模块提供了一些有用的函数帮助获取对象的信息，例如模块、类、方法、函数、回溯、帧对象以及代码对象。例如它可以帮助你检查类的内容，获取某个方法的源代码，取得并格式化某个函数的参数列表，或者获取你需要显示的回溯的详细信息。

该模块提供了4种主要的功能：类型检查、获取源代码、检查类与函数、检查解释器的调用堆栈。

类型和成员

getmembers() 函数获取对象的成员，例如类或模块。函数名以"is"开始的函数主要作为 getmembers() 的第2个参数使用。它们也可用于判定某对象是否有如下的特殊属性:

类型	属性	描述
module -- 模块	__doc__	文档字符串
	__file__	文件名(内置模块没有文件名)
class -- 类	__doc__	文档字符串
	__name__	类定义时所使用的名称
	__qualname__	qualified name -- 限定名称
	__module__	该类型被定义时所在的模块的名称
method -- 方法	__doc__	文档字符串
	__name__	该方法定义时所使用的名称
	__qualname__	qualified name -- 限定名称
	__func__	实现该方法的函数对象
	__self__	该方法被绑定的实例，若没有绑定则为 None
	__module__	定义此方法的模块的名称
function -- 函数	__doc__	文档字符串
	__name__	用于定义此函数的名称
	__qualname__	qualified name -- 限定名称
	__code__	包含已编译函数的代码对象 bytecode
	__defaults__	所有位置或关键字参数的默认值的元组
	__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
回溯	tb_frame	此级别的框架对象
	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)
框架	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	原始编译字节码的字符串
	co_cellvars	单元变量名称的元组(通过包含作用域引用)
	co_consts	字节码中使用的常量元组
	co_filename	创建此代码对象的文件的名称
	co_firstlineno	number of first line in Python source code
	co_flags	bitmap of CO_* flags, read more here
	co_lnotab	编码的行号到字节码索引的映射
	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	定义此代码对象的名称
	co_names	tuple of names other than arguments and function locals
	co_nlocals	局部变量的数量
	co_stacksize	需要虚拟机堆栈空间
	co_varnames	参数名和局部变量的元组
generator -- 生成器	__name__	名称
	__qualname__	qualified name -- 限定名称
	gi_frame	框架
	gi_running	生成器在运行吗？
	gi_code	code
	gi_yieldfrom	object being iterated by yield from, or None
coroutine -- 协程	__name__	名称
	__qualname__	qualified name -- 限定名称
	cr_await	object being awaited on, or None
	cr_frame	框架
	cr_running	is the coroutine running?
	cr_code	code
	cr_origin	where coroutine was created, or None. See sys.set_coroutine_origin_tracking_depth()
builtin	__doc__	文档字符串
	__name__	此函数或方法的原始名称
	__qualname__	qualified name -- 限定名称
	__self__	instance to which a method is bound, or None

在 3.5 版更改: 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.

在 3.7 版更改: Add cr_origin attribute to coroutines.

在 3.10 版更改: Add __builtins__ attribute to functions.

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.

注解

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.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.

在 3.3 版更改: 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.

在 3.8 版更改: Functions wrapped in functools.partial() 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).

3.5 新版功能.

在 3.8 版更改: Functions wrapped in functools.partial() now return True if the wrapped function is a coroutine function.

inspect.iscoroutine(object)

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

3.5 新版功能.

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:

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

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

3.5 新版功能.

inspect.isasyncgenfunction(object)

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

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

3.6 新版功能.

在 3.8 版更改: Functions wrapped in functools.partial() now return True if the wrapped function is a asynchronous generator function.

inspect.isasyncgen(object)

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

3.6 新版功能.

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.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, but 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().

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.

在 3.5 版更改: 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.

inspect.getsourcefile(object)

Return the name of the Python source 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.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.

在 3.3 版更改: 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.

在 3.3 版更改: 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

3.3 新版功能.

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 inspect.get_annotations(). The global, locals, and eval_str parameters are passed into inspect.get_annotations() when resolving the annotations; see the documentation for inspect.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 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.

3.5 新版功能: follow_wrapped parameter. Pass False to get a signature of callable specifically (callable.__wrapped__ will not be used to unwrap decorated callables.)

3.10 新版功能: globals, locals, and eval_str parameters.

注解

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.

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, is the "return" annotation of the callable.

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

在 3.5 版更改: Signature objects are 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.

在 3.7 版更改: 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'"

classmethod from_callable(obj, *, follow_wrapped=True, globalns=None, localns=None)

Return a Signature (or its subclass) object for a given callable obj. Pass follow_wrapped=False to get a signature of obj without unwrapping its __wrapped__ chain. globalns and localns will be used as the namespaces when resolving annotations.

This method simplifies subclassing of Signature:

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

3.5 新版功能.

3.10 新版功能: globalns and localns parameters.

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() to create a modified copy.

在 3.5 版更改: Parameter objects are 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.

在 3.6 版更改: These parameter names are 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. Possible values (accessible via Parameter, like Parameter.KEYWORD_ONLY):

名称	含意
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 a enum value of Parameter.kind.

3.8 新版功能.

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'"

在 3.4 版更改: 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.

注解

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.

在 3.9 版更改: 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.

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': ()}

3.5 新版功能.

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)

参见

PEP 362 - Function Signature Object.

The detailed specification, implementation details and examples.

类与函数

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.getargspec(func)

Get the names and default values of a Python function's parameters. A named tuple ArgSpec(args, varargs, keywords, defaults) is returned. args is a list of the parameter names. varargs and keywords are the names of the * and ** parameters or None. defaults is a tuple of default argument values or None if there are no default arguments; if this tuple has n elements, they correspond to the last n elements listed in args.

3.0 版后已移除: Use getfullargspec() for an updated API that is usually a drop-in replacement, but also correctly handles function annotations and keyword-only parameters.

Alternatively, use signature() and Signature Object, which provide a more structured introspection API for callables.

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.

在 3.4 版更改: This function is now based on signature(), but still ignores __wrapped__ attributes and includes the already bound first parameter in the signature output for bound methods.

在 3.6 版更改: This method was previously documented as deprecated in favour of 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 getargspec() API.

在 3.7 版更改: 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.

inspect.getargvalues(frame)

Get information about arguments passed into a particular frame. A 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.

注解

This function was inadvertently marked as deprecated in Python 3.5.

inspect.formatargspec(args[, varargs, varkw, defaults, kwonlyargs, kwonlydefaults, annotations[, formatarg, formatvarargs, formatvarkw, formatvalue, formatreturns, formatannotations]])

Format a pretty argument spec from the values returned by getfullargspec().

The first seven arguments are (args, varargs, varkw, defaults, kwonlyargs, kwonlydefaults, annotations).

The other six arguments are functions that are called to turn argument names, * argument name, ** argument name, default values, return annotation and individual annotations into strings, respectively.

例如:

>>> from inspect import formatargspec, getfullargspec
>>> def f(a: int, b: float):
...     pass
...
>>> formatargspec(*getfullargspec(f))
'(a: int, b: float)'

3.5 版后已移除: Use signature() and Signature Object, which provide a better introspecting API for callables.

inspect.formatargvalues(args[, varargs, varkw, locals, formatarg, formatvarargs, formatvarkw, formatvalue])

Format a pretty argument spec from the four values returned by getargvalues(). The format* arguments are the corresponding optional formatting functions that are called to turn names and values into strings.

注解

This function was inadvertently marked as deprecated in Python 3.5.

inspect.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.

inspect.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'

3.2 新版功能.

3.5 版后已移除: Use Signature.bind() and Signature.bind_partial() instead.

inspect.getclosurevars(func)

Get the mapping of external name references in a Python function or method func to their current values. A 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.

TypeError is raised if func is not a Python function or method.

3.3 新版功能.

inspect.unwrap(func, *, stop=None)

Get the object wrapped by func. It follows the chain of __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, signature() uses this to stop unwrapping if any object in the chain has a __signature__ attribute defined.

ValueError is raised if a cycle is encountered.

3.4 新版功能.

inspect.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 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 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 eval() on those values:

• If eval_str is true, eval() is called on values of type str. (Note that get_annotations doesn't catch exceptions; if 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 eval(); see the documentation for 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 对象注解属性的最佳实践 for more information on annotations best practices.

3.10 新版功能.

The interpreter stack

When the following functions return "frame records," each record is a named tuple FrameInfo(frame, filename, lineno, function, code_context, index). The tuple contains the frame object, the filename, the line number of the current line, the function name, a list of lines of context from the source code, and the index of the current line within that list.

在 3.5 版更改: Return a named tuple instead of a tuple.

注解

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 finally clause. This is also important if the cycle detector was disabled when Python was compiled or using 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 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.

inspect.getframeinfo(frame, context=1)

Get information about a frame or traceback object. A named tuple Traceback(filename, lineno, function, code_context, index) is returned.

inspect.getouterframes(frame, context=1)

Get a list of frame records 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.

在 3.5 版更改: A list of named tuples FrameInfo(frame, filename, lineno, function, code_context, index) is returned.

inspect.getinnerframes(traceback, context=1)

Get a list of frame records 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.

在 3.5 版更改: A list of named tuples FrameInfo(frame, filename, lineno, function, code_context, index) is returned.

inspect.currentframe()

Return the frame object for the caller's stack frame.

CPython implementation 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.

inspect.stack(context=1)

Return a list of frame records 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.

在 3.5 版更改: A list of named tuples FrameInfo(frame, filename, lineno, function, code_context, index) is returned.

inspect.trace(context=1)

Return a list of frame records 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.

在 3.5 版更改: A list of named tuples FrameInfo(frame, filename, lineno, function, code_context, index) is returned.

Fetching attributes statically

Both getattr() and hasattr() can trigger code execution when fetching or checking for the existence of attributes. Descriptors, like properties, will be invoked and __getattr__() and __getattribute__() may be called.

For cases where you want passive introspection, like documentation tools, this can be inconvenient. getattr_static() has the same signature as getattr() but avoids executing code when it fetches attributes.

inspect.getattr_static(obj, attr, default=None)

Retrieve attributes without triggering dynamic lookup via the descriptor protocol, __getattr__() or __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 __dict__ is shadowed by another member (for example a property) then this function will be unable to find instance members.

3.2 新版功能.

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

Current State of Generators and Coroutines

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. getgeneratorstate() allows the current state of a generator to be determined easily.

inspect.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.

3.2 新版功能.

inspect.getcoroutinestate(coroutine)

Get current state of a coroutine object. The function is intended to be used with coroutine objects created by 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.

3.5 新版功能.

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:

inspect.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 locals() in the body of the generator, and all the same caveats apply.

If generator is a generator with no currently associated frame, then an empty dictionary is returned. TypeError is raised if generator is not a Python generator object.

CPython implementation 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.

3.3 新版功能.

inspect.getcoroutinelocals(coroutine)

This function is analogous to getgeneratorlocals(), but works for coroutine objects created by async def functions.

3.5 新版功能.

Code Objects Bit Flags

Python code objects have a co_flags attribute, which is a bitmap of the following flags:

inspect.CO_OPTIMIZED

The code object is optimized, using fast locals.

inspect.CO_NEWLOCALS

If set, a new dict will be created for the frame's f_locals when the code object is executed.

inspect.CO_VARARGS

The code object has a variable positional parameter (*args-like).

inspect.CO_VARKEYWORDS

The code object has a variable keyword parameter (**kwargs-like).

inspect.CO_NESTED

The flag is set when the code object is a nested function.

inspect.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.

inspect.CO_NOFREE

The flag is set if there are no free or cell variables.

inspect.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.

3.5 新版功能.

inspect.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.

3.5 新版功能.

inspect.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.

3.6 新版功能.

注解

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 inspect module for any introspection needs.

命令行界面

The inspect module also provides a basic introspection capability from the command line.

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.

--details

Print information about the specified object rather than the source code