1 # 如果想要运用[]取值，可以实现__getitem__()
2 # 想要运用[]设值，可以实现__setitem__()
3 # 若想通过del与[]来删除，可以实现__delitem__()
4 class ChainMap:
5 def __init__(self,*maps):
6 self.maps=maps
7 def lookup(self,key): # 查找是否有对应键的字典
8 for m in self.maps:
9 if key in m:
10 return m
11 return None
12 def __getitem__(self, item): # 实现__getitem__()方法
13 m=self.lookup(item)
14 if m:
15 return m[item]
16 else:
17 raise KeyError
18 def __setitem__(self, key, value): # 实现__setitem__()方法
19 m=self.lookup(key)
20 if m:
21 m[key]=value
22 else:
23 self.maps[key]=value
24 def __delitem__(self, key): # 实现__delitem__()方法
25 m=self.lookup(key)
26 if m:
27 del m[key]
28 else:
29 raise KeyError
30 c=ChainMap({'A':'Justin'},{'A':'Monica','B':'Irene'})
31 print(c.maps)
32 print(c['A'])
33 c['A']='caterpillar'
34 print(c.maps)
35 del c['A']
36 print(c.maps)
