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This article mainly shows you "how to add sub-context to ChainMap in python", which is easy to understand and clear. I hope it can help you solve your doubts. Let me lead you to study and learn "how to add sub-context to ChainMap in python".

Description

1. ChainMap implements the subcontext. New _ child ().

2. This method can choose to take the mapping as a parameter and return a new ChainMap instance, including the input mapping, and then all the current mappings in the underlying chain map.

Example

> > from collections import ChainMap > mom = {"name": "Jane", "age": 31} > dad = {"name": "John", "age": 35} > family = ChainMap (mom, dad) > familyChainMap ({'name':' Jane', 'age': 31}, {' name': 'John',' age': 35}) > > son = {"name": "Mike" "age": 0} > family = family.new_child (son) > for person in family.maps:... Print (person)... {'name':' Mike', 'age': 0} {' name': 'Jane',' age': 31} {'name':' John', 'age': 35}

Here,. New_child () returns a new object son that contains the new mapping, followed by the old mapping, mom, and dad. Note that the new mapping now occupies the first place in the internal mapping list. Maps .

With .new _ child (), you can create a subcontext that you can update without changing any existing mappings.

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