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标题:
Python运算符重载
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作者:
kinganeng
时间:
2009-10-16 10:17
标题:
Python运算符重载
2009年08月13日 星期四 06:48 P.M.
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[key]，
For If
__len__ 长度 len(X)
__cmp__ 比较 X==Y,X
Python代码
[/url]
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
[url=http://wangtong40.javaeye.com/blog/369429#]
class
indexer:
def
__getitem__(self, index):
#iter override
return
index ** 2
X = indexer()
X[2]
for
i
in
range(5):
print
X
class indexer:
def __getitem__(self, index): #iter override
return index ** 2
X = indexer()
X[2]
for i in range(5):
print X
7.3 索引重载
Python代码
[/url]
class
stepper:
def
__getitem__(self, i):
return
self.data
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
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
[url=http://wangtong40.javaeye.com/blog/369429#]
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
7.5 打印重载
Python代码
[/url]
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__
7.6 Call调用函数重载
Python代码
[url=http://wangtong40.javaeye.com/blog/369429#]
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)
7.7 析构函数重载
Python代码
[/url]
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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