How Can I Make Global Variables Accessible Across Imported Python Modules?

Visibility of Global Variables in Imported Modules

The problem stems from the limited visibility of global variables in Python modules. Globals are accessible within their containing module but not across different modules. This becomes an issue when importing modules and attempting to reference variables from the importing module.

Solutions

There are several approaches to make global variables visible to imported modules:

• Declare the Variable in the Imported Module:

  • Explicitly assign the variable within the imported module.
  • Example: module1.f(a=3)

• Set the Variable in the Importing Module:

  • Assign the variable to the importing module.
  • Example: import module1; module1.a = 3; module1.f()

• Create a Shared Module:

  • Define the variable in a separate module that is imported by both the main module and the imported module.
  • Example: import shared_stuff; shared_stuff.a = 3; import module1; module1.f()

• Modify the Builtin Module:

  • Only applicable in rare cases where global scope is required.
  • Example: import builtins; builtins.a = 3; import module1; module1.f()

Caution regarding Cyclic Imports

Importing a module that references another module can lead to cyclic imports and runtime errors. Avoid this by selectively importing specific functions or classes instead of the entire module.

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