python中的dir()函數(shù)是一個非常重要的函數(shù)，它可以幫助我們查看函數(shù)的功能和特性。

中文說明：不帶參數(shù)時，返回當前范圍內的變量、方法和定義的類型列表；帶參數(shù)時，返回參數(shù)的屬性、方法列表。如果參數(shù)包含方法__dir__()，該方法將被調用。如果參數(shù)不包含__dir__()，該方法將最大限度地收集參數(shù)信息。

參數(shù)object： 對象、變量、類型。

版本：該函數(shù)在python各個版本中都有，但是每個版本中顯示的屬性細節(jié)有所不同。使用時注意區(qū)別。

例如

>>>import struct>>>dir() # show the names in the module namespace[’__builtins__’,’__doc__’,’__name__’,’struct’]>>>dir(struct) # show the names in the struct module[’Struct’,’__builtins__’,’__doc__’,’__file__’,’__name__’, ’__package__’,’_clearcache’,’calcsize’,’error’,’pack’,’pack_into’, ’unpack’,’unpack_from’]>>>class Shape(object): def __dir__(self): return [’area’,’perimeter’,’location’]>>> s= Shape()>>>dir(s)

[’area’, ’perimeter’, ’location’]Note Because dir() is supplied primarily as a convenience for use at an interactive prompt, it tries to supply an interesting set of names more than it tries to supply a rigorously or consistently defined set of names, and its detailed behavior may change across releases. For example, metaclass attributes are not in the result list when the argument is a class.

代碼實例

>>>dir()[’__builtins__’,’__doc__’,’__name__’,’__package__’]>>>import struct>>>dir()[’__builtins__’,’__doc__’,’__name__’,’__package__’,’struct’]>>>dir(struct)[’Struct’,’__builtins__’,’__doc__’,’__file__’,’__name__’,’__package__’,’_clearcache’,’calcsize’,’error’,’pack’,’pack_into’,’unpack’,’unpack_from’]>>>class Person(object):... def __dir__(self):... return ['name','age','country']...>>>dir(Person)[’__class__’,’__delattr__’,’__dict__’,’__dir__’,’__doc__’,’__format__’,’__getattribute__’,’__hash__’,’__init__’,’__module__’,’__new__’,’__reduce__’,’__reduce_ex__’,’__repr__’,’__setattr__’,’__sizeof__’,’__str__’,’__subclasshook__’,’__weakref__’]>>> tom= Person()>>>dir(tom)[’age’,’country’,’name’]

知識點擴展：

help()函數(shù)的作用

在使用python來編寫代碼時，會經常使用python自帶函數(shù)或模塊，一些不常用的函數(shù)或是模塊的用途不是很清楚，這時候就需要用到help函數(shù)來查看幫助。

這里要注意下，help()函數(shù)是查看函數(shù)或模塊用途的詳細說明，而dir()函數(shù)是查看函數(shù)或模塊內的操作方法都有什么，輸出的是方法列表。

怎么使用help函數(shù)查看python模塊中函數(shù)的用法

help()括號內填寫參數(shù)，操作方法很簡單。例如：

>>> help(’dir’)Help on built-in function dir in module builtins:dir(...) dir([object]) -> list of strings If called without an argument, return the names in the current scope. Else, return an alphabetized list of names comprising (some of) the attributes of the given object, and of attributes reachable from it. If the object supplies a method named __dir__, it will be used; otherwise the default dir() logic is used and returns: for a module object: the module’s attributes. for a class object: its attributes, and recursively the attributes of its bases. for any other object: its attributes, its class’s attributes, and recursively the attributes of its class’s base classes.

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