python 特殊方法

python 特殊方法

1. 简介

   * python 中一切皆对象
   * 特殊方法:
     1.以双下划线开头,并以双下划线结尾
     2.__方法名__,例如: __init__
     3.可以通过dir()查看

2. 实例操作

   //查看特殊方法
   >>> dir(list)
   ['__add__', '__class__', '__contains__', '__delattr__', '__delitem__', '__delslice__', '__doc__', '__eq__', '__format__', '__ge__', '__getattribute__', '__getitem__', '__getslice__', '__gt__', '__hash__', '__iadd__', '__imul__', '__init__', '__iter__', '__le__', '__len__', '__lt__', '__mul__', '__ne__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__reversed__', '__rmul__', '__setattr__', '__setitem__', '__setslice__', '__sizeof__', '__str__', '__subclasshook__', 'append', 'count', 'extend', 'index', 'insert', 'pop', 'remove', 'reverse', 'sort']
   
   //运算符(对象.特殊方法)
   >>> 'nihao' + 'beijing'
   'nihaobeijing'
   >>> 'nihao'.__add__('beijing')
   'nihaobeijing'
   
   >>> 1.1 * 8
   8.8
   >>> 1.1.__mul__(8)
   8.8
   
   //列表(对象.特殊方法)
   >>> a = [1,2,3,4]
   >>> len(a)
   4
   >>> a.__len__()
   4
   
   >>> a[3]
   4
   >>> a.__getitem__(3)
   4
   
   >>> a[0] = 9
   >>> a
   [9, 2, 3, 4]
   >>> a.__setitem__(0,10)
   >>> a
   [10, 2, 3, 4]
   
   //函数
   >>> class A(object):         
   ...     def __call__(self,a):
   ...         return a + 10
   ...
   >>> b = A()
   >>> print(b(1))
   11
   
   >>> map(b,[1,2,3,4,5])
   [11, 12, 13, 14, 15]