python 闭包

#不是闭包
def f1():
    a = 10 
    def f2():
        a = 20 
        print(a)
    print(a)  -- 10
    f2() -- 20
    print(a)  --10
f1()

___

闭包

def f1():
    a = 10
    def f2():
        c = 20 * a
    return f2
f = f1()
print(f.__closure__)

---

origin=0

def factory(pos):
    def go(step):
        nonlocal pos 
        new_pos = pos + step
        pos = new_pos
        return new_pos
    return  go


t = factory(origin)
print(t(2))
--2
print(t(3))
--5
print(t(5))
--10
print(origin)
--0