Python运算符重载用法实例分析

本文实例讲述了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。