Global reassignment Python example

foobar.py

def foo(x):
    return x

def reassign(y):
    # Must have this line to tell the interpreter that you mean the outer 'foo' reference, not a new, locally scoped one.
    global foo
    if y:
        foo = lambda x: x + 1
    else:
        foo = lambda x: x - 1

if __name__ == "__main__":
    print(foo(1))
    reassign(True)
    print(foo(1))
    reassign(False)
    print(foo(1))