Question

The __debug__ variable is handy in part because it affects every module. If I want to create another variable that works the same way, how would I do it?

The variable (let’s be original and call it ‘foo’) doesn’t have to be truly global, in the sense that if I change foo in one module, it is updated in others. I’d be fine if I could set foo before importing other modules and then they would see the same value for it.

Answer 1

I don’t endorse this solution in any way, shape or form. But if you add a variable to the __builtin__ module, it will be accessible as if a global from any other module that includes __builtin__ — which is all of them, by default.

a.py contains

print foo 

b.py contains

import __builtin__ __builtin__.foo = 1 import a 

The result is that ‘1’ is printed.

Edit: The __builtin__ module is available as the local symbol __builtins__ — that’s the reason for the discrepancy between two of these answers. Also note that __builtin__ has been renamed to builtins in python3.