How to Dynamically Assign enum Values from a Variable in Python

Discover a simple way to dynamically assign values to `enum` members in Python without using global variables. Learn how to implement it using the `aenum` package!
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How to Dynamically Assign enum Values from a Variable in Python

Enums in Python provide developers with a way to create enumerated constants that can be more readable than regular constants. However, a common challenge arises when you want to assign enum values dynamically based on other variables, particularly when working with classes that manage complex functionalities, like HTTP sessions. This post dives into a specific problem and a solution using the aenum package to handle enum assignments dynamically.

The Problem

You might be familiar with the scenario where you have an HttpMethod enum that defines your HTTP methods using the requests library methods. Here is a similar setup:

[[See Video to Reveal this Text or Code Snippet]]

However, when you need to switch to using methods of a session instance instead of the global requests functions, things get complicated. You want to avoid making the session a global variable but still be able to use it inside your enum.

The attempted approach looked something like this:

[[See Video to Reveal this Text or Code Snippet]]

The goal was to create an enum that used session.get or session.post, but without creating any unnecessary global variables. This led to some confusion regarding implementations like using __ignore__ or __init_subclass__ without success.

The Solution: Using aenum

After some exploration, the solution emerged using the aenum package which provides enhanced functionality for enums. The key was using the __ignore__ field along with creating an instance of the necessary class within the enum definition itself. Here's how you can implement this:

Step-by-Step Implementation

Define the HttpPooling Class: Ensure you have your HTTP pooling class set up correctly:

[[See Video to Reveal this Text or Code Snippet]]

Create the Enum with Dynamic Values: Use the aenum package to define your enum with dynamic values for each HTTP method:

[[See Video to Reveal this Text or Code Snippet]]

What Does This Code Achieve?

Dynamic Method Linking: Each member of the HttpMethod enum now correctly points to a method on the HttpPooling session instance.

Flexibility: You can now easily call HttpMethod.GET() to make a GET request using the session, making the structure maintainable and clean.

Conclusion

By leveraging the capabilities provided by the aenum package, it's possible to create enums in Python that assign values dynamically based on instance variables, avoiding complications from global variables. This solution not only solves the problem at hand but also maintains a clean structure within your code, allowing for easy expansions or modifications in the future.

If you find yourself needing dynamic enums in your Python applications, remember to check out the aenum package for similar cases, and streamline your process.

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