On: PEP 810 – Explicit lazy imports

[flykespice]

Side-effect means you're changing state outside the scope the code is running.

Sure thing you can declare globals variable and run anything on a module file global scope (outside funcs and class body), but even that 'global' scope is just an illusion, and everything declared there, as yourself said, is scoped to the module's namespace

(and you can't leak the 'globals' when importing the module unless you explicity do so 'from foo import *'. Think of python's import as eval but safer because it doesn't leaks the results from the module execution)

So for a module to have side-effect (for me) it would either:

- Change/Create attributes from other modules

- Call some other function that does side-effect (reflection builtins? IO stuff)

[IshKebab → flykespice]

Often it's things like registering functions in a global registry, or patching things about how Python works (e.g. adding stuff to the module path).

[kstrauser → flykespice]

You’re right. “Side effect” here means that your program’s behavior changes simply by importing something, eg by monkey patching something else.

If’s not:

* Importing other modules.

* Taking a long time to import.

* Writing .pyc files.

If any program can “import foo” and still execute exactly the same bytecode afterward as before, you can say that foo doesn’t have side effects.