global和nonlocal混合使用

def scope_test():
    def do_local():
        spam = "local spam" #此函数定义了另外的一个spam字符串变量，并且生命周期只在此函数内。此处的spam和外层的spam是两个变量，如果写出spam = spam + “local spam” 会报错
    def do_nonlocal():
        nonlocal  spam        #使用外层的spam变量
        spam = "nonlocal spam"
    def do_global():
        global spam
        spam = "global spam"
    spam = "test spam"
    do_local()
    print("After local assignmane:", spam)
    do_nonlocal()
    print("After nonlocal assignment:",spam)
    do_global()
    print("After global assignment:",spam)
 
scope_test()
print("In global scope:",spam)

After local assignment: test spam
After nonlocal assignment: nonlocal spam
After global assignment: nonlocal spam
In global scope: global spam

global声明的是第一层环境中的变量（全局变量）。

nonlocal声明的是外部嵌套函数内的变量，只改变外层函数中的变量。