access python global variable in a nested function

Question

I' am a beginner in python language. I've got a headache in understanding how global variables work. this is a specific example that doesn't make sense to me:

def func():
    def nested():
        global x
        x=1
    print(x)

func()

this throws :global name 'x' is not defined

Why is x is not available even though it has been made global in the nested function?

It's not really the global. x is only defined in a function you never call, but you try to print it. Try calling nested() before printing and the global will get defined. — Mark
– Mark, Commented Jul 12, 2020 at 23:03
yes. Because it isn't defined. Why do you expect it to be defined? nested is never called anywhere. — juanpa.arrivillaga
– juanpa.arrivillaga, Commented Jul 12, 2020 at 23:03
@MarkMeyer thank you. the global x inside a function won't define a variable outside unless it's called. I get it now. — Mouad Maaziz
– Mouad Maaziz, Commented Jul 12, 2020 at 23:09

Javad Rezaei · Accepted Answer · 2020-07-12 23:05:25Z

3

you have to call nested() to define global variable x. ithout calling it, there is no definition of variable x and so you will have error!

def func():
    def nested():
        global x
        x=1
    nested()
    print(x)

func()

answered Jul 12, 2020 at 23:05

Javad Rezaei

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