# 28.13. `inspect` — 检查对象

2.1 新版功能.

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。

## 28.13.1. 类型和成员

The `getmembers()` function retrieves the members of an object such as a class or module. The sixteen 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:

类型 | 属性 | 描述 | Notes
--- | --- | --- | ---
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 |
| __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 |
| im_class | class object that asked for this method | (1)
| im_func or __func__ | 实现该方法的函数对象 |
| im_self or __self__ | 该方法被绑定的实例，若没有绑定则为 `None` |
function – 函数 | __doc__ | 文档字符串 |
| __name__ | 用于定义此函数的名称 |
| func_code | 包含已编译函数的代码对象 bytecode |
| func_defaults | tuple of any default values for arguments |
| func_doc | (same as __doc__) |
| func_globals | global namespace in which this function was defined |
| func_name | (same as __name__) |
generator – 生成器 | __iter__ | defined to support iteration over container |
| close | raises new GeneratorExit exception inside the generator to terminate the iteration |
| gi_code | code object |
| gi_frame | frame object or possibly `None` once the generator has been exhausted |
| gi_running | set to 1 when generator is executing, 0 otherwise |
| next | return the next item from the container |
| send | resumes the generator and “sends” a value that becomes the result of the current yield-expression |
| throw | used to raise an exception inside the generator |
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_exc_traceback | traceback if raised in this frame, or `None` |
| f_exc_type | exception type if raised in this frame, or `None` |
| f_exc_value | exception value if raised in this frame, or `None` |
| 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 * or ** args) |
| co_code | 原始编译字节码的字符串 |
| 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: 1=optimized `|` 2=newlocals `|` 4=*arg `|` 8=**arg |
| co_lnotab | 编码的行号到字节码索引的映射 |
| co_name | 定义此代码对象的名称 |
| co_names | 局部变量名称的元组 |
| 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 |
builtin | __doc__ | 文档字符串 |
| __name__ | 此函数或方法的原始名称 |
| __self__ | instance to which a method is bound, or `None` |

Note:

1. 在 2.2 版更改: `im_class` used to refer to the class that defined the method.

`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()` does not return metaclass attributes when the argument is a class (this behavior is inherited from the `dir()` function).

`inspect.``getmoduleinfo`(path)

  Return a tuple of values that describe how Python will interpret the file identified by path if it is a module, or `None` if it would not be identified as a module. The return tuple is `(name, suffix, mode, module_type)`, where name is the name of the module without the name of any enclosing package, suffix is the trailing part of the file name (which may not be a dot-delimited extension), mode is the `open()` mode that would be used (`'r'` or `'rb'`), and module_type is an integer giving the type of the module. module_type will have a value which can be compared to the constants defined in the `imp` module; see the documentation for that module for more information on module types.

  在 2.6 版更改: Returns a named tuple `ModuleInfo(name, suffix, mode, module_type)`.

`inspect.``getmodulename`(path)

  Return the name of the module named by the file path, without including the names of enclosing packages. This uses the same algorithm as the interpreter uses when searching for modules. If the name cannot be matched according to the interpreter’s rules, `None` is returned.

`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 or unbound 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.

  2.6 新版功能.

`inspect.``isgenerator`(object)

  Return true if the object is a generator.

  2.6 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.

  2.6 新版功能.

`inspect.``ismethoddescriptor`(object)

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

  This is new as of Python 2.2, and, 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 `im_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.

  2.3 新版功能.

`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`.

  2.5 新版功能.

`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`.

  2.5 新版功能.

## 28.13.2. Retrieving source code

`inspect.``getdoc`(object)

  Get the documentation string for an object, cleaned up with `cleandoc()`.

`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).

`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 `IOError` 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 `IOError` 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.

  2.6 新版功能.

## 28.13.3. 类与函数

`inspect.``getclasstree`(classes[, unique])

  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 arguments. A tuple of four things is returned: `(args, varargs, keywords, defaults)`. args is a list of the argument names (it may contain nested lists). varargs and keywords are the names of the `*` and `**` arguments 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.

  在 2.6 版更改: Returns a named tuple `ArgSpec(args, varargs, keywords, defaults)`.

`inspect.``getargvalues`(frame)

  Get information about arguments passed into a particular frame. A tuple of four things is returned: `(args, varargs, keywords, locals)`. args is a list of the argument names (it may contain nested lists). varargs and keywords are the names of the `*` and `**` arguments or `None`. locals is the locals dictionary of the given frame.

  在 2.6 版更改: Returns a named tuple `ArgInfo(args, varargs, keywords, locals)`.

`inspect.``formatargspec`(args[, varargs, varkw, defaults, formatarg, formatvarargs, formatvarkw, formatvalue, join])

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

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

  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.

`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,)}
      >>> getcallargs(f, a=2, x=4)
      {'a': 2, 'named': {'x': 4}, 'b': 1, 'pos': ()}
      >>> getcallargs(f)
      Traceback (most recent call last):
      ...
      TypeError: f() takes at least 1 argument (0 given)

  2.7 新版功能.

## 28.13.4. The interpreter stack

When the following functions return “frame records,” each record is a tuple of six items: 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.

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

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])

  Get information about a frame or traceback object. A 5-tuple is returned, the last five elements of the frame’s frame record.

  在 2.6 版更改: Returns a named tuple `Traceback(filename, lineno, function, code_context, index)`.

`inspect.``getouterframes`(frame[, context])

  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.

`inspect.``getinnerframes`(traceback[, context])

  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.

`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])

  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.

`inspect.``trace`([context])

  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.