python怎么查看帮助函数

不带参数时，返回当前范围内的变量、方法和定义的类型列表；带参数时，返回参数的属性、方法列表。如果参数包含方法__dir__()，

该方法将被调用。如果参数不包含__dir__()，该方法将限度地收集参数信息。

>>>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)

>>>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']