Duplicate output when calling a custom function from the same file?

[road2knowledge]

Hi folks,

I'm new to programming and python, and I don't understand why if you call a custom function from the same file it's defined in, you get duplicate output.

e.g. a file "question.py" containing the following:

def double(number):
    return number * 2

from question import double
print(double(1))

And if I were to manually input "double(2)" after running the module, the output seems perfectly normal (just one 4).
Why is that? And is there a way to avoid the duplicate apart from calling the function from a separate py file?

I know this must have been asked before, but I couldn't find it via forum search or Google (the queries all return questions related to list modification).

Thanks in advance for clearing up my confusion!