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Python

Puffy wuff
Puffy wuff
9,573 Points

Python scope question

Why does this work:

def outer():
    x = 100
    def inner():
        print(x)
    inner()

outer()

But not this:

def outer():
    x = 100
    def inner():
        x += 10
        print(x)
    inner()

outer()

I don't understand why I can print x from the outer scope but not update it.

1 Answer

Steven Parker
Steven Parker
229,607 Points

The "print" is simply accessing the variable from the outer scope.

But when you make an assignment, Python takes that to mean that a new variable should be created in the current scope. But "+=" is a special kind of assignment that also accesses the current value, so it doesn't work with variables being created in the same statement.