Python: modifying enclosing variable in function

Question

Are there any ways to modify the enclosing variables with functions written outside of the main function?

I want to do this:

def modify_a():
    nonlocal a
    a =+ 1

def process_abc(some_criteria):
    a, b, c = generate(some_criteria)
    modify_a()
    return a, b, c

a, b, c = process_abc()

I tried the following, but I wonder if there's a way to make the above work. If there's any, is it bad coding practice?

def modify_a(a=a):
    a =+ 1

def process_abc(some_criteria):
    a, b, c = generate(some_criteria)
    a = modify_a(a)
    return a, b, c

a, b, c = process_abc()

a is in no sense an "enclosing variable" here. You'd have to actually put the definition of modify_a inside the definition of process_abc() for that to be true. — jasonharper
– jasonharper, Commented Jan 17, 2022 at 16:24

Bharel · Accepted Answer · 2022-01-17 16:18:50Z

1

The only way to do it is by modifying the parent frame.

Either way, this is a very bad idea. Functions are a form of encapsulation.

If you wish to modify the parent data, you can pass a mutable structure like so:

def modify_a(a=a):
    a[0] =+ 1

def process_abc(some_criteria):
    a, b, c = generate(some_criteria)
    a= [a]
    a = modify_a(a)[0]
    return a, b, c

a, b, c = process_abc()

It is generally frowned upon though.

answered Jan 17, 2022 at 16:18

Bharel

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