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Python : How to assign new value from outside of the function but the value is inside a function

September 2, 2022

Why val can’t access inside bar after declare new val’s value inside bar?

def foo() -> None:
        val = 'not change yet'
        def bar() -> None:
            print(val)        # Error: local variable 'val' referenced before assignment
            val = 'changed'
            print(val)
        bar()
foo()

How can I overcome the issue?
PS: I don’t want to put val outside foo.

>Solution :

You should define val as nonlocal.

def foo() -> None:
        val = 'not change yet'
        def bar() -> None:
            nonlocal val
            print(val)        # Error: local variable 'val' referenced before assignment
            val = 'changed'
            print(val)
        bar()
foo()

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