[转] Python运算符重载
运算符重载在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，
For If
__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
[*]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
7.2 迭代重载
Python代码
[*]class indexer:
[*] def __getitem__(self, index): #iter override
[*] return index ** 2
[*]X = indexer()
[*]X
[*]for i in range(5):
[*] print X
class indexer: def __getitem__(self, index): #iter override return index ** 2X = indexer()Xfor i in range(5): print X
7.3 索引重载
Python代码
[*]class stepper:
[*] def __getitem__(self, i):
[*] return self.data
[*]
[*]X = stepper()
[*]X.data = 'Spam'
[*]X #call __getitem__
[*]
[*]for item in X: #call __getitem__
[*] print item
class stepper: def __getitem__(self, i): return self.data X = stepper()X.data = 'Spam'X #call __getitem__for item in X: #call __getitem__ print item
7.4 getAttr/setAttr重载
Python代码
[*]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__ = 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,attrnameX = empty()print X.age #call__getattr__class accesscontrol: def __setattr__(self, attr, value): if attr == 'age': # Self.attrname = value loops! self.__dict__ = 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
[*]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 += otherclass 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
[*]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 * otherp = Prod(2) #call __init__print p(1) #call __call__print p(2)
7.7 析构函数重载
Python代码
[*]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__
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