How to Implement Cross-Module Variables in Python: A Practical Guide

How to Establish a Cross-Module Variable

As highlighted by the popularity of the debug variable, there's a practical need for variables accessible across multiple modules within a project. To address this, let's explore a solution for creating a custom "foo" variable with similar cross-module capabilities.

Unlike __debug__, our "foo" variable doesn't require real-time global updates across modules. Instead, it suffices to set its value before importing other modules.

Solution: Global Module-Level Variables

To establish a cross-module variable, we can define it as a global variable at the module level. This ensures that any modifications made to it within one module will be reflected in imports of that module by other scripts.

Example:

• a.py:

  <code class="python">var = 1</code>

• b.py:

  <code class="python">import a
  print(a.var)
  import c
  print(a.var)</code>

• c.py:

  <code class="python">import a
  a.var = 2</code>

When running python b.py, the output will be:

1
2

This demonstrates how modifying a.var in c.py also affects its value in b.py when they share the same import context.

Real-World Applications

Global module-level variables find practical use in frameworks like Django, where settings are stored centrally in the global_settings.py module and accessible throughout the project via django.conf.settings.

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