在python語言中提供了類似於c++的運算子重在功能：
一下為python運算子重在呼叫的方法如下：
method overloads call for
__init__ 建構函式 x=class()
__del__ 析構函式 物件銷毀
__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__ 呼叫函式 x()
__getattr_ 限制 x.undefine
__setattr__ 取值 x.any=value
__getitem__ 索引 x[key]，
__len__ 長度 len(x)
__cmp__ 比較 x==y,x
__lt__ 小於 x
__eq__ 等於 x=y
__radd__ right-side + +x
__iadd__ += x+=y
__iter__ 迭代 for in
1. 減法過載
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. 迭代過載
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. 索引過載
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過載
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. 列印過載
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呼叫函式過載
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. 析構函式過載
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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