confused by python3 closure

Question

this code

def gen(x):
    def f():
        return x

    return f

print(gen(1)())

works well.

but when i run this code,

def gen(x):
    def f():
        x += 1
        return x

    return f

print(gen(1)())

I got an error shows that

UnboundLocalError: local variable 'x' referenced before assignment

what happened to it? and How to understand the closure of python3 .

score 2 · Accepted Answer · answered Mar 23 '13 at 03:50

2

def gen(x):
    def f():
        nonlocal x # add this line
        x += 1
        return x

    return f

print(gen(1)())

answered Mar 23 '13 at 03:50

HYRY

1 Answers1