inspect --- 檢查對象¶
inspect 子產品提供了一些有用的函數幫助擷取對象的資訊,例如子產品、類、方法、函數、回溯、幀對象以及代碼對象。例如它可以幫助你檢查類的内容,擷取某個方法的源代碼,取得并格式化某個函數的參數清單,或者擷取你需要顯示的回溯的詳細資訊。
該子產品提供了4種主要的功能:類型檢查、擷取源代碼、檢查類與函數、檢查解釋器的調用堆棧。
類型和成員¶
getmembers() 函數擷取對象的成員,例如類或子產品。函數名以"is"開始的函數主要作為 getmembers() 的第2個參數使用。它們也可用于判定某對象是否有如下的特殊屬性:
類型
屬性
描述
module 子產品
__doc__
文檔字元串
__file__
檔案名(内置子產品沒有檔案名)
class -- 類
__doc__
文檔字元串
__name__
類定義時所使用的名稱
__qualname__
qualified name -- 限定名稱
__module__
該類型被定義時所在的子產品的名稱
method 方法
__doc__
文檔字元串
__name__
該方法定義時所使用的名稱
__qualname__
qualified name -- 限定名稱
__func__
實作該方法的函數對象
__self__
該方法被綁定的執行個體,若沒有綁定則為 None
__module__
name of module in which
this method was defined
function -- 函數
__doc__
文檔字元串
__name__
用于定義此函數的名稱
__qualname__
qualified name -- 限定名稱
__code__
包含已編譯函數的代碼對象 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.
__module__
name of module in which
this function was defined
回溯
tb_frame
此級别的架構對象
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)
架構
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
原始編譯位元組碼的字元串
co_cellvars
單元變量名稱的元組(通過包含作用域引用)
co_consts
位元組碼中使用的常量元組
co_filename
建立此代碼對象的檔案的名稱
co_firstlineno
number of first line in
Python source code
co_flags
bitmap of CO_* flags,
read more here
co_lnotab
編碼的行号到位元組碼索引的映射
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
定義此代碼對象的名稱
co_names
局部變量名稱的元組
co_nlocals
局部變量的數量
co_stacksize
需要虛拟機堆棧空間
co_varnames
參數名和局部變量的元組
generator -- 生成器
__name__
名稱
__qualname__
qualified name -- 限定名稱
gi_frame
架構
gi_running
生成器在運作嗎?
gi_code
code
gi_yieldfrom
object being iterated by
yield from, or
None
coroutine -- 協程
__name__
名稱
__qualname__
qualified name -- 限定名稱
cr_await
object being awaited on,
or None
cr_frame
架構
cr_running
is the coroutine running?
cr_code
code
cr_origin
builtin
__doc__
文檔字元串
__name__
此函數或方法的原始名稱
__qualname__
qualified name -- 限定名稱
__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.
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 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.
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.
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.
inspect.isasyncgen(object)¶
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 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 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)¶
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
Accepts a wide range of Python callables, from plain functions and classes to
functools.partial() objects.
Raises ValueError if no signature can be provided, and
TypeError if that type of object is not supported.
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.)
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.
classinspect.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'"
classmethodfrom_callable(obj, *, follow_wrapped=True)¶
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.
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.
classinspect.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):
名稱
含義
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, 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.
classinspect.BoundArguments¶
Result of a Signature.bind() or Signature.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 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.
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', ())])
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)
參見
PEP 362 - Function Signature Object.The detailed specification, implementation details and examples.
類與函數¶
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 版後已移除: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 版後已移除: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.
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.
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.
指令行界面¶
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