why I don't need to import the supporting modules?

Question

The get_square_root() function relies on the math module. To call the get_square_root() function in analysis.py, I don't need to import the math module, why is that?


# calculator.py

import math

def get_square_root(a):
    return math.sqrt(a)

#analysis.py

import calculator

calculator.get_square_root(5)

Something I know about import in python (Correct me if I understood sth. wrong). When import calculator, the Python interpreter reads the whole calculator.py module, but the objects in the module not to be accessed by <ModuleName>.<ObjectName>. This is how I call the get_square_root() in analysis.py. But how the get_square_root() access math since there no math in analysis.py ?

"why I don't need to import the math module" - because you're not using it. — goodvibration, Mar 04 '20 at 20:51
@zvone thanks.. but the code still works when I only import the function as `from calculator import get_square_root` and call `get_square_root(5)` — baicai, Mar 04 '20 at 21:07
This is related to scoping. See [Short description of the scoping rules?](https://stackoverflow.com/q/291978/4518341) Python also something special with modules to make star imports work, though I'm not sure what exactly. — wjandrea, Mar 04 '20 at 21:32

score 1 · Answer 1 · answered Mar 05 '20 at 02:02

When you run calculator in any way, math is bound in its module scope, making it accessible to get_square_root.

When you run import calculator in analysis, math is still in the module scope for get_square_root, plus calculator is bound in the scope of analysis so you can access it as calculator.math.

When you run from calculator import get_square_root in analysis, math is still in the module scope for get_square_root, but you cannot access it from analysis since calculator is not bound.

P.s. let me know if any of my terminology is wrong. I'm still a bit shaky on scoping. — wjandrea, Mar 05 '20 at 02:03

why I don't need to import the supporting modules?

1 Answers1