在Python语言中提供了类似于C++的运算符重在功能：
一下为Python运算符重在调用的方法如下：
Method        Overloads        Call for
__init__        构造函数        X=Class()
__del__        析构函数        对象销毁
__add__        +                X+Y,X+=Y
__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<Y
__lt__        小于            X<Y
__eq__        等于            X=Y
__radd__        Right-Side +        +X
__iadd__        +=                X+=Y
__iter__        迭代            For In
7.1    减法重载

Python代码

1. class Number:   
2.     def __init__(self, start):   
3.         self.data = start   
4.     def __sub__(self, other): #minus method   
5.         return Number(self.data – other)   
6.   
7. number = Number(20)   
8. 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

7.2    迭代重载

Python代码

1. class indexer:   
2.     def __getitem__(self, index): #iter override   
3.         return index ** 2  
4. X = indexer()   
5. X[2]   
6. for i in range(5):   
7.     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]

7.3    索引重载

Python代码

1. class stepper:   
2.     def __getitem__(self, i):   
3.         return self.data[i]   
4.       
5. X = stepper()   
6. X.data = ‘Spam’  
7. X[1] #call __getitem__   
8.   
9. for item in X: #call __getitem__   
10.     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

7.4    getAttr/setAttr重载

Python代码

1. class empty:   
2.     def __getattr__(self,attrname):   
3.         if attrname == ‘age’:   
4.             return 40  
5.         else:   
6.             raise AttributeError,attrname   
7. X = empty()   
8. print X.age #call__getattr__   
9.   
10. class accesscontrol:   
11.     def __setattr__(self, attr, value):   
12.         if attr == ‘age’:   
13.             # Self.attrname = value loops!   
14.             self.__dict__[attr] = value   
15.         else:   
16.             print attr   
17.             raise AttributeError, attr + ‘not allowed’  
18.   
19. X = accesscontrol()   
20. X.age = 40      #call __setattr__   
21. 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 

7.5    打印重载

Python代码

1. class adder:   
2.     def __init__(self, value=0):   
3.         self.data = value   
4.     def __add__(self, other):   
5.         self.data += other   
6.   
7. class addrepr(adder):   
8.     def __repr__(self):   
9.         return ‘addrepr(%s)’ % self.data   
10.       
11. x = addrepr(2)  #run __init__   
12. x + 1       #run __add__   
13. print x     #run __repr__  

class adder: def __init__(self, value=0): self.data = value def __add__(self, other): self.data += other class addrepr(adder): def __repr__(self): return 'addrepr(%s)' % self.data x = addrepr(2) #run __init__ x + 1 #run __add__ print x #run __repr__

7.6    Call调用函数重载

Python代码

1. class Prod:   
2.     def __init__(self, value):   
3.         self.value = value   
4.     def __call__(self, other):   
5.         return self.value * other   
6.   
7. p = Prod(2) #call __init__   
8. print p(1) #call __call__   
9. print p(2)  

class Prod: def __init__(self, value): self.value = value def __call__(self, other): return self.value * other p = Prod(2) #call __init__ print p(1) #call __call__ print p(2)

7.7    析构函数重载

Python代码

1. class Life:   
2.     def __init__(self, name=‘name’):   
3.         print ‘Hello’, name   
4.         self.name = name   
5.     def __del__(self):   
6.         print ‘Goodby’, self.name   
7.   
8. brain = Life(‘Brain’) #call __init__   
9. brain = ‘loretta’    # call __del__