Скачать или смотреть Changing Variable Values Before Importing a Module in Python

Learn how to change the value of a variable in Python before importing a module, ensuring efficient testing and development.
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This video is based on the question https://stackoverflow.com/q/72461140/ asked by the user 'Aman Ahmed Siddiqui' ( https://stackoverflow.com/u/16938256/ ) and on the answer https://stackoverflow.com/a/72461231/ provided by the user 'quamrana' ( https://stackoverflow.com/u/4834/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Changing Variable Values Before Importing a Module in Python: A Practical Guide

Developing applications in Python often requires testing various code components without altering the original source files. One common challenge developers face is modifying the value of a variable in a module before it's imported, especially in testing scenarios where direct changes aren't permitted. This guide will help you understand how to effectively change variable values in imported modules, using a practical example.

The Problem: Importing Modules and Variable Scope

Imagine you have a config.py file containing several configuration variables like this:

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

Then you have another file, game.py, that imports these variables:

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

Now, during testing (when you're likely making multiple runs to verify your code), you want to modify the MONEY variable without being able to change config.py or game.py. This is a common scenario and can be a bit tricky.

The Solution: Modify the Module Directly

In order to change the MONEY variable without modifying the original files, you need to import the entire configuration module instead of importing individual variables. Follow these steps:

Step 1: Modify the game.py to Use the Config Module Directly

Instead of importing MONEY directly, import the entire config module in your game.py:

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

This change allows you to reference MONEY through config rather than as an independent variable.

Step 2: Update Your Test Script

Next, adjust your testing script test.py to modify the MONEY variable within the config module:

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

Expected Output

When you run test.py, you should see output reflecting the changed value of MONEY:

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

Conclusion

By following these steps, you can successfully alter the values in your configuration module before importing and using them in your application files. This approach ensures your original source files remain untouched while allowing flexibility during testing.

Key Takeaways

Use import module_name instead of from module import variable for the modules you want to manipulate.

Modify the variables directly within the module in your test scripts before calling functions that use them.

This functionality can save you time and effort in the testing process, leading to a smoother development experience in Python. Happy coding!