python有帮助函数么

>>>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.

>>>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']