Python运算符重载用法实例分析
作者：adupt
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。