(转)inspect — Inspect live objects
原文:https://docs.python.org/3/library/inspect.html
中文:https://www.rddoc.com/doc/Python/3.6.0/zh/library/inspect/?highlight=inspect
关于python中inspect模块的一些探究----------https://blog.csdn.net/weixin_35955795/article/details/53053762
The 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.
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:
Type | Attribute | Description |
---|---|---|
module | __doc__ | documentation string |
__file__ | filename (missing for built-in modules) | |
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 |
|
function | __doc__ | documentation string |
__name__ | name with which this function was defined | |
__qualname__ | qualified name | |
__code__ | code object containing compiled function 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 | |
__annotations__ | mapping of parameters names to annotations;"return" key is reserved for return annotations. |
|
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_restricted | 0 or 1 if frame is in restricted execution mode | |
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 here |
|
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_kwonlyargcount | number of keyword only arguments (not including ** arg) | |
co_name | name with which this code object was defined | |
co_names | tuple of names of local variables | |
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 . Seesys.set_coroutine_origin_tracking_depth() |
|
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 |
Changed in version 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.
Changed in version 3.7: Add cr_origin
attribute to coroutines.
inspect.
getmembers
(object[, predicate])-
Return all the members of an object in a list of (name, value) pairs sorted by name. If the optional predicateargument 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.
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.
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).New in version 3.5.
inspect.
iscoroutine
(object)-
Return true if the object is a coroutine created by an
async def
function.New 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:
def gen():
yield
@types.coroutine
def gen_coro():
yield assert not isawaitable(gen())
assert isawaitable(gen_coro())New 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)
TrueNew in version 3.6.
inspect.
isasyncgen
(object)-
Return true if the object is an asynchronous generator iterator created by an asynchronous generatorfunction.
New 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.
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()
orisbuiltin()
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 passesismethod()
.
inspect.
isdatadescriptor
(object)-
Return true if the object is a data descriptor.
Data descriptors have both a
__get__
and a__set__
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 returnFalse
.
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 returnFalse
.
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.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.
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.
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.
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
New in version 3.3.
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)-
Return a
Signature
object for the givencallable
:>>>>>> 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.Raises
ValueError
if no signature can be provided, andTypeError
if that type of object is not supported.New in version 3.5:
follow_wrapped
parameter. PassFalse
to get a signature ofcallable
specifically (callable.__wrapped__
will not be used to unwrap decorated callables.)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.
- 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 itsparameters
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.Changed in version 3.5: 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.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 aTypeError
.
bind_partial
(*args, **kwargs)-
Works the same way as
Signature.bind()
, but allows the omission of some required arguments (mimicsfunctools.partial()
behavior.) ReturnsBoundArguments
, or raises aTypeError
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/orreturn_annotation
to override the corresponding properties of the base signature. To remove return_annotation from the copied Signature, pass inSignature.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) -
Return a
Signature
(or its subclass) object for a given callableobj
. Passfollow_wrapped=False
to get a signature ofobj
without unwrapping its__wrapped__
chain.This method simplifies subclassing of
Signature
:class MySignature(Signature):
pass
sig = MySignature.from_callable(min)
assert isinstance(sig, MySignature)New in version 3.5.
- 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.Changed in version 3.5: 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.Changed in version 3.6: 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
, likeParameter.KEYWORD_ONLY
):Name Meaning POSITIONAL_ONLY Value must be supplied as a positional argument.
Python has no explicit syntax for defining positional-only parameters, but many built-in and extension module functions (especially those that accept only one or two parameters) accept them.
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
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, passParameter.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'"Changed in version 3.4: In Python 3.3 Parameter objects were allowed to have
name
set toNone
if theirkind
was set toPOSITIONAL_ONLY
. This is no longer permitted.
- class
inspect.
BoundArguments
-
Result of a
Signature.bind()
orSignature.bind_partial()
call. Holds the mapping of arguments to the function’s parameters.arguments
-
An ordered, mutable mapping (
collections.OrderedDict
) of parameters’ names to arguments’ values. Contains only explicitly bound arguments. Changes inarguments
will reflect inargs
andkwargs
.Should be used in conjunction with
Signature.parameters
for any argument processing purposes.Note
Arguments for which
Signature.bind()
orSignature.bind_partial()
relied on a default value are skipped. However, if needed, useBoundArguments.apply_defaults()
to add them.
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
OrderedDict([('a', 'spam'), ('b', 'ham'), ('args', ())])New in version 3.5.
The
args
andkwargs
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)
See also
- PEP 362 - Function Signature Object.
- The detailed specification, implementation details and examples.
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.
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 orNone
. defaults is a tuple of default argument values orNone
if there are no default arguments; if this tuple has n elements, they correspond to the last n elements listed in args.Deprecated since version 3.0: 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 orNone
if arbitrary positional arguments are not accepted. varkw is the name of the**
parameter orNone
if arbitrary keyword arguments are not accepted. defaults is an n-tuple of default argument values corresponding to the last npositional parameters, orNone
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 2inspect
module API.Changed in version 3.4: 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.Changed in version 3.6: 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 legacygetargspec()
API.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.
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 orNone
. locals is the locals dictionary of the given frame.Note
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.For example:
>>> from inspect import formatargspec, getfullargspec
>>> def f(a: int, b: float):
... pass
...
>>> formatargspec(*getfullargspec(f))
'(a: int, b: float)'Deprecated since version 3.5: 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.Note
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. wheneverfunc(*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'New in version 3.2.
Deprecated since version 3.5: Use
Signature.bind()
andSignature.bind_partial()
instead.
inspect.
getclosurevars
(func)-
Get the mapping of external name references in a Python function or method func to their current values. Anamed 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.New in version 3.3.
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.New in version 3.4.
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.
Changed in version 3.5: Return a named tuple instead of a 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 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.
Changed in version 3.5: 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.
Changed in version 3.5: 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.
Changed in version 3.5: 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.
Changed in version 3.5: 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.New in version 3.2.
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.
New in version 3.2.
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 hascr_running
andcr_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.
New in version 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:
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.
New in version 3.3.
inspect.
getcoroutinelocals
(coroutine)-
This function is analogous to
getgeneratorlocals()
, but works for coroutine objects created byasync def
functions.New in version 3.5.
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.
New in version 3.5.
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 canyield from
coroutine objects. See PEP 492 for more details.New in version 3.5.
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.
New in version 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 inspect
module for any introspection needs.
Command Line Interface
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
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