python: collections.chainmap

import collections
 
# 初始化字典
dict1 = { 'a' : 1, 'b' : 2 }
dict2 = { 'b' : 3, 'c' : 4 }
 
# 初始化ChainMap
chain = collections.ChainMap(dict1, dict2)
 
# 使用maps输出chainMap
print(chain.maps)  # [{'b': 2, 'a': 1}, {'b': 3, 'c': 4}]
 
# 输出key
print(list(chain.keys()))  # ['b', 'c', 'a']
 
# 输出值
print(list(chain.values())) # [2, 4, 1]
 
# 访问
print(chain['b'])  # 2
print(chain.get('b'))  # 2
 
# 使用new_child添加新字典
dict3 = { 'f' : 5 }
new_chain = chain.new_child(dict3)
print (new_chain.maps)  # [{'f': 5}, {'b': 2, 'a': 1}, {'b': 3, 'c': 4}]
 
new_chain.maps = reversed(new_chain.maps)
print(new_chain.maps)