# Python中运算符重载的使用分析

Python中运算符重载是如何来使用的呢？下面的内容将会通过具体的实例来演示Python中运算符重载的使用方法及相关技巧：

__init__ 构造函数 X=Class()
__del__ 析构函数 对象销毁
__or__ | X|Y,X|=Y
__repr__ 打印转换 print X，repr(X)
__str__ 打印转换 print X，str(X)
__call__ 调用函数 X()
__getattr_ 限制 X.undefine
__setattr__ 取值 X.any=value
__getitem__ 索引 X[key]，
__len__ 长度 len(X)
__cmp__ 比较 X==Y,X

1. 减法重载

 1234567891011121314 class Number:   def __init__(self, start):     self.data = start   def __sub__(self, other): #minus method     return Number(self.data - other) number = Number(20) y = number – 10 # invoke __sub__ method class Number:   def __init__(self, start):     self.data = start   def __sub__(self, other): #minus method     return Number(self.data - other) number = Number(20) y = number – 10 # invoke __sub__ method

2. 迭代重载

 1234567891011121314 class indexer:   def __getitem__(self, index): #iter override     return index ** 2 X = indexer() X[2] for i in range(5):   print X[i] class indexer:   def __getitem__(self, index): #iter override     return index ** 2 X = indexer() X[2] for i in range(5):   print X[i]

3. 索引重载

 12345678910111213141516 class stepper:   def __getitem__(self, i):     return self.data[i] X = stepper() X.data = 'Spam' X[1] #call __getitem__ for item in X: #call __getitem__   print item class stepper:   def __getitem__(self, i):     return self.data[i] X = stepper() X.data = 'Spam' X[1] #call __getitem__ for item in X: #call __getitem__    print item

4. getAttr/setAttr重载

 1234567891011121314151617181920212223242526272829303132333435363738 class empty:   def __getattr__(self,attrname):     if attrname == 'age':       return 40     else:       raise AttributeError,attrname X = empty() print X.age #call__getattr__ class accesscontrol:   def __setattr__(self, attr, value):     if attr == 'age':       # Self.attrname = value loops!       self.__dict__[attr] = value     else:       print attr       raise AttributeError, attr + 'not allowed' X = accesscontrol() X.age = 40   #call __setattr__ X.name = 'wang' #raise exception class empty:   def __getattr__(self,attrname):     if attrname == 'age':       return 40     else:       raise AttributeError,attrname X = empty() print X.age #call__getattr__ class accesscontrol:   def __setattr__(self, attr, value):     if attr == 'age':       # Self.attrname = value loops!       self.__dict__[attr] = value     else:       print attr       raise AttributeError, attr + 'not allowed' X = accesscontrol() X.age = 40   #call __setattr__ X.name = 'wang' #raise exception

5. 打印重载