global variables from separate functions?

Asked Oct 01 '15 at 10:32

Active Oct 01 '15 at 10:32

Viewed 14 times

I've been trying to understand the behaviour of global variables in Python. From here, I gather that I can read any variable defined in an outer scope. If I want to modify it in an inner scope, I have to "declare" as global in that inner scope, so that Python looks for it according to its scoping rules and knows I'm not creating a new local variable.

But why does the following correctly print the values of variables a and b?

import sys

def func1():
    print a # will print 1
    print b # will print 2
    return

def main():
    global a 
    a = 1
    global b
    b = 2
    func1()
    return 0

if __name__ == '__main__':
    status = main()
    sys.exit(status)

edited May 23 '17 at 12:06

Community

asked Oct 01 '15 at 10:32

Ricky Robinson

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Because those variables *are* `global`...!? – deceze Oct 01 '15 at 10:36
So it's not only a matter of scope: I just have to declare it as global somewhere in my code, and I can access it everywhere? – Ricky Robinson Oct 01 '15 at 10:37
You declare `global a`, so Python sets it as global variable. The same as if you had declared the variable outside the function in the first place. – deceze Oct 01 '15 at 10:39
Does python use both dynamic and lexical scope? – Ricky Robinson Oct 01 '15 at 10:39
Yes, you can use it everywhere(except out of this file :P) – Remi Guan Oct 01 '15 at 10:39
OK, great! I thought it only worked in the way described in the first link in my post. – Ricky Robinson Oct 01 '15 at 10:40
And you also can write `global a` everywhere, only need before you define the `a`. – Remi Guan Oct 01 '15 at 10:40

global variables from separate functions?

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