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This article mainly shows you "how ChainMap manages default parameter values 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 ChainMap manages default parameter values in python".

1. Default parameter values in ChainMap management methods and functions.

2. The ChainMap object takes kwargs and defaults as parameters. This order ensures that it is provided manually in the instance class.

Parameter takes precedence over the defaults value.

Example

Suppose you are writing an application that manages your company's employee data. You have the following categories to represent a general user:

In some cases, you need to add a functional worker to access different components of the CRM system. Your first idea is to modify user to add new features. But this may make the class too complex, so you decide to create a subclass CRMUser to provide the required functionality.

This class takes the user name and CRMcomponent as parameters. It also needs some kwargs. You want to do this through CRMUser providing reasonable default values for the initializer of the base class without losing the * * kwargs. The following is the ChainMap that solves the problem in the following ways:

From collections import ChainMap class CRMUser (User): def _ init__ (self, name, component, * * kwargs): defaults = {"user_id": next (component.user_id), "role": "read"} super (). _ init__ (name, * * ChainMap (kwargs, defaults))

In this code example, you will create user. Class initialization, taking name, component, and * * kwargs as parameters. Then, you create a local dictionary, including user_id and the default value role. Then. _ _ init__ () uses super (). In this call, your name is transferred directly to the parent's initializer and uses chain mapping to provide default values for other parameters.

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