NameError when calling an imported function requiring something defined in the current environment

Question

I have two Python files:

b.py :

def buzz():
    foobar = Foobar()

c.py :

from b import buzz

class Foobar:
    pass

buzz()

Running python c.py raises:

NameError: name 'Foobar' is not defined

Looks like there is a basic Python's import mechanism I still don't understand. I would expect that, when buzz() is called, it has dynamically access to the environment now containing Foobar .

---

Of course (?), if I replace the importation of buzz by its definition, it works:

d.py :

def buzz():
    foobar = Foobar()

class Foobar:
    pass

buzz()

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Context.

This may be an XY-problem. Ultimately, I want to be able to change the behaviour of buzz depending on which Foobar variant has previously been imported. However, I would be interested in understanding why b.py / c.py fails.

Answer 1

buzz function's definition is in module "b.py". This means when the body of the buzz is being executed( buzz() in c.py), interpreter jumps into module b . Module b 's global namespace is where body of the buzz function can access global variables not c 's global namespace and of course there is no "Foobar" in module b 's globals() .

In LEGB rule, "G" points to the module's global namespace which the interpreter is currently in, not other modules' global namespace.