class A(object):
def __init__(self,num):
self.num = num
self.start_num = -1
def __len__(self):
'''
@summary: 當使用len(Test)該對象時調用該方法,當沒有該方法是會報錯,且返回數據不爲整數也會報錯
'''
print "__len__"
return self.num - self.start_num - 1
if __name__ == "__main__":
print len(A(10))
輸出:__len__
10
__reversed__():當使用reversed函數翻轉對象時調用
class A(object):
def __init__(self,num):
self.num = num
def __reversed__(self):
'''
@summary: 當使用reversed函數翻轉對象時調用
'''
ret = []
for i in range(self.num):
ret.append(self.num - i-1)
return ret
if __name__ == "__main__":
print reversed(A(10))
輸出:[9, 8, 7, 6, 5, 4, 3, 2, 1, 0]
__contains__():當使用in,not in 對象的時候 調用(not in 是在in完成後再取反,實際上還是in操作)
class A(object):
def __init__(self,num):
self.num = num
def __contains__(self, item):
'''
@summary:當使用in,not in 對象的時候 ,not in 是在in完成後再取反,實際上還是in操作
'''
print "__contains__:%s is in?"%item
if item < self.num and item >= 0:
return True
return False
if __name__ == "__main__":
if 3 in A(10):print "True"
else:print False
if 3 not in A(10):print "True"
else:print False
輸出:__contains__:3 is in?
True
__contains__:3 is in?
False