8、nonlocal和global的区别

一：global关键字用来在函数或其它局部作用域中使用全局变量。但是如果不使用全局变量也可以不适用global关键字声明。
二：nonlocal关键字用来在函数或其它作用域中使用外层（非全局）变量

def scope_test():
    def do_local():
        spam = "local spam"  # 局部变量不会改变scope_test的spam值

    def do_nonlocal():
        nonlocal spam  # nonlocal 它会改变scope_test的spam值
        spam = "nonlocal spam"

    def do_global():
        global spam  # 会改变模块层级的绑定
        spam = "global spam"

    spam = "test spam"
    do_local()
    print("1:", spam)
    do_nonlocal()
    print("2:", spam)
    do_global()
    print("3:", spam)


scope_test()
print("4:", spam)

结果：

1: test spam
2: nonlocal spam
3: nonlocal spam
4: global spam