How does Python know I want to double number I did not define? (Beginner)

Question

x = 10
def double(y):
    return 2 * x
print(double(x))

Output is 20 As far as I know, it should return None because in function "double" I double x which is undefined that block.

If the variable isn't defined in the function, it searches the containing scopes. — Barmar, Nov 20 '20 at 22:44
If you remove `x=10` and use `print(double(10))` you'll get the NameError you "wanted". Nice first question. — Patrick Artner, Nov 20 '20 at 22:49

score 2 · Answer 1 · answered Nov 20 '20 at 22:44

2

x is defined outside of the function scope as a global variable that is also available in the function

answered Nov 20 '20 at 22:44

Tamir

score 1 · Answer 2 · answered Nov 20 '20 at 22:44

1

It is because x is a global variable, so when you call double it is just multiplying x by 2 no matter what if you were to say put

x = 10
def double(y):
    return 2 * x
print(double(40))

you would still get 20 as you are returning the variable x multiplied by 2.

answered Nov 20 '20 at 22:44

ConnerWithAnE

It also would not return None it would throw an error because 2 multiplied by None is not possible. – ConnerWithAnE Nov 20 '20 at 22:46

2 Answers2