print('呼叫父類建構函式')
def parentmethod(self):
print('呼叫父類方法')
def setattr(self, attr):
self.parentattr = attr
def getattr(self):
print('父類屬性：', self.parentattr)
def __del__(self):
print('父類析構')
class child(parent):
def __init__(self):
print('呼叫子類建構函式')
def childmethod(self):
print('呼叫子類方法 child method')
def __del__(self):
print('子類析構')
def __str__(self):
return 'class name:child'
def __repr__(self):
return 'classname:child'
c = child()
c.childmethod()
c.parentmethod()
c.setattr(200)
c.getattr()
if isinstance( c, parent ):
print('yes')
if issubclass( child, parent ):
print('yes')
#del c
print(repr(c)) #輸出classname:child，repr(c)會呼叫c.__repr__(self)
print(str(c)) #輸出class name:child，str(c)會呼叫c.__str__(self)
參考：
7.1 減法過載
class number:
def __init__(self, start):
self.data = start
def __sub__(self, other): #minus method
return number(self.data - other)
def show(self):
print(self.data)
number = number(20)
y = number - 10 # invoke __sub__ method
y.show() #輸出10
7.2 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]) #x[i]呼叫x.__getitem__(i)
7.3 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)
'''輸出：sp
am'''7.4 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__
print(x.__dict__)
x.name = 'wang' #raise exception
7.5 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__ 輸出addrepr(3)
7.6 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__ 輸出2
print (p(2)) #輸出4
7.7 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__，輸出hello brain
brain = 'loretta' # call __del__ ，輸出goodby brain，brain指向了別的物件，原來的類物件要釋放，
故呼叫析構函式
7.8 加法函式過載
class test(object):
def __init__(self, value):
self.value = value
def __add__(self, x):
return self.value + x.value
a = test(3)
b = test(4)
print (a + b)
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