from collections import ChainMap

"""

     相当于join两个dict的操作

"""

# 示例1

dict1 = {"a": 1, "b": 2}

dict2 = {"c": 3, "d": 4}

chain_dict = ChainMap(dict1, dict2)

for k, v in chain_dict.items():

    print(k, v)

'''

打印结果:

c 3

d 4

a 1

b 2

'''

print('-' * 50)

# 示例2

dict1 = {"a": 1, "b": 2}

dict2 = {"b": 3, "d": 4}

chain_dict = ChainMap(dict1, dict2)

for k, v in chain_dict.items():

    print(k, v)

'''

打印结果: b只出现了一次,就是首次的值

b 2

d 4

a 1

'''

print('-' * 50)

# 示例3

dict1 = {"a": 1, "b": 2}

dict2 = {"c": 3, "d": 4}

chain_dict = ChainMap(dict1, dict2)

chain_dict.update({'e': 8})

for k,v in chain_dict.items():

    print(k,v)

'''

c 3

d 4

a 1

b 2

e 8

'''

print('-' * 50)

# 示例4

dict1 = {"a": 1, "b": 2}

dict2 = {"c": 3, "d": 4}

chain_dict = ChainMap(dict1, dict2)

print(chain_dict)

# Remove and return an item pair from maps[0]. Raise KeyError is maps[0] is empty.'  感觉没啥用

item = chain_dict.popitem()

print(item)  # ('b', 2)

# pop也只能弹出chain_map[0]中的元素,有点鸡

value = chain_dict.pop('a')

print(value)  #

print(chain_dict)    # ChainMap({}, {'c': 3, 'd': 4})

print('-' * 50)

dict1 = {"a": 1, "b": 2}

dict2 = {"c": 3, "d": 4}

chain_dict = ChainMap(dict1, dict2)

# new_chain_dict = chain_dict.new_child()

# print(new_chain_dict)  # ChainMap({}, {'a': 1, 'b': 2}, {'c': 3, 'd': 4})  , 这有啥用呀

# 在chain_map添加一个新的dict

new_chain_dict = chain_dict.new_child({'name':'admin'})

print(new_chain_dict)  # ChainMap({'name': 'admin'}, {'a': 1, 'b': 2}, {'c': 3, 'd': 4})