python如何查看帮助函数
python中的助手函数dir()
中文说明：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__()，该方法将最大限度地收集参数信息。
参数object： 对象、变量、类型。
版本：该函数在python各个版本中都有，但是每个版本中显示的属性细节有所不同。使用时注意区别。
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.
代码实例
>>>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']
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