Python运算符重载用法实例分析

本文实例讲述了python/' target='_blank'>python运算符重载用法。分享给大家供大家参考。具体如下：

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

1. 减法重载

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

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

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

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

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__ 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__

6. Call调用函数重载

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) 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. 析构函数重载

class Life:    def __init__(self, name='name'):      print 'Hello', name      self.name = name    def __del__(self):      print 'Goodby', self.name  brain = Life('Brain') #call __init__  brain = 'loretta'  # call __del__

希望本文所述对大家的Python程序设计有所帮助。