Python3 variables in functions

Question

def a():
    b = 1
    def x():
        b -= 1
    if something is something:
        x()
a()

What im wanting here is to change b from a() in x() I have tried using;

def a():
    b = 1
    def x():
        global b
        b -= 1
    if something is something:
        x()

a()

But this, as I expected, this told me global b is not defined.

b needs to change after x() is has run and if x() is called a second time b needs to be what x() set it to - 0 not what it was originally set to in a() - 1.

donkopotamus · Accepted Answer · 2015-11-02 00:12:50Z

3

In order to alter the value of a variable defined in a containing scope, use nonlocal. This keyword is similar to intent to global (which indicates the variable should be considered to be the binding in the global scope).

So try something like:

def a():
    b = 1
    def x():
        # indicate we want to be modifying b from the containing scope
        nonlocal b
        b -= 1
    if something is something:
        x()

a()

edited Nov 2, 2015 at 0:12

answered Nov 2, 2015 at 0:08

donkopotamus

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2 Comments

user4341854 Over a year ago

Could you elaborate at all on what non local is exactly. Very new to Python (well programming in general)

user4341854 Over a year ago

Than you, that explanation was perfect

Justice · Accepted Answer · 2015-11-02 00:08:36Z

1

This should work:

def a():
    b = 1
    def x(b):
        b -= 1
        return b
    b = x(b)
    return b
a()

answered Nov 2, 2015 at 0:08

Justice

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1 Comment

user4341854 Over a year ago

Thanks but I was hoping for a way to do it without using 'return'

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