Python 中的内部 function 中传输变量的差异

Question

In Python, is there a difference between the following two codes both of which gives the same result c = [0,-10]?

def foo1():
    a = [0,1]

    def foo2():
        a[1] = -10

    foo2()
    return a


c = foo1()

and

def foo1():
    a = [0,1]

    def foo2(b):
        b[1] = -10

    foo2(a)
    return a


c = foo1()

Some commentator suggests this is answered by this question . But it does not since my question asks about the passing of variables through an inner function whilst the linked question does not.

Answer 1

In the first, a is a free variable whose value is taken from the nearest enclosing scope (in this case, the scope of foo1 ) that defines a .

In the second, b is a local variable initialized using the argument passed to foo2 when it is called, which is the variable a defined in foo1 .

In each case, you assign -10 to the second "slot" of the same list.