import module : global variable within function

Question

There are two py files. util.py

def add_sum():
    print(x + 3)

test.py

from util import *
x=3
add_sum()

When I run test.py, I get error:

Traceback (most recent call last):
File "test.py", line 45, in <module>
    add_sum()
File "util.py", line 10, in add_sum
    print(x + 3)
NameError: name 'x' is not defined

The variable x is global, why function cannot reach x and raise error?

Does this answer your question? Python importing variables from other file — Thomas Schillaci
– Thomas Schillaci, Commented Mar 12, 2020 at 8:17
@ThomasSchillaci there are som differences. I can unterstand the Python importing variables from other file . really to know is after import, the add_sum function is not just like define in new file test? — tranquil.coder
– tranquil.coder, Commented Mar 12, 2020 at 8:38

bruno desthuilliers · Accepted Answer · 2020-03-12 08:38:50Z

2

Python's "globals" are only globals to the module they are defined in. That's by design - you should only use globals when you really can't avoid them, as it makes the code harder to understand, test and maintain.

In your case, the proper way is to explicitely pass x to your function:

 # util.py
 def add_sum(x):
     return x + 3

And

# test.py
# NB: star imports are evil too, for the very same reasons
from util import add_sum
x=3
print(add_sum(x))

answered Mar 12, 2020 at 8:38

bruno desthuilliers

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