運算符重載
在Python語言中提供了類似于C++的運算符重在功能：
一下為Python運算符重在調用的方法如下：
Method Overloads Call for
__init__ 構造函數 X=Class()
__del__ 析構函數 對象銷毀
__add__ + X+Y,X+=Y
__or__ | X|Y,X|=Y
__repr__ 列印轉換 print X，repr(X)
__str__ 列印轉換 print X，str(X)
__call__ 調用函數 X()
__getattr_ 限制 X.undefine
__setattr__ 取值 X.any=value
__getitem__ 索引 X[key]，
For If
__len__ 長度 len(X)
__cmp__ 比較 X==Y,X
__lt__ 小于 X
__eq__ 等于 X=Y
__radd__ Right-Side + +X
__iadd__ += X+=Y
__iter__ 疊代 For In
7.1 減法重載
Python代碼
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 疊代重載
Python代碼
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 ** 2X = indexer()X[2]for i in range(5): print X[i]
7.3 索引重載
Python代碼
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
7.4 getAttr/setAttr重載
Python代碼
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,attrnameX = 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 列印重載
Python代碼
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調用函數重載
Python代碼
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 析構函數重載
Python代碼
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__