闭包

闭包 = 函数 + 环境变量
实例：

def curve_pre():
    a = 25

    def curve(x):
        return a * x * x

    return curve

a = 10
f = curve_pre()
print(f.__closure__)	# (<cell at 0x0000000002595BE8: int object at 0x000007FED8E77400>,)
print(f.__closure__[0].cell_contents)	# 25 查看环境变量 验证是否是闭包
print(f(2))		# 100

global 把局部变量转换成全局变量
nonlocal 声明变量不是局部变量
实例：

origin = 0

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

t = position(origin)
print(t(2))		# 2
print(t(3))		# 5
print(t(5))		# 10

有记忆现场的功能