【python】global的使用

global a
def cc():
    a = 1
    a += 1
    print(a)
cc()
print(a)

出现错误：NameError: name ‘a‘ is not defined

count_1 = 1
count_2 = 2
count_3 = 3


def cc():
    global count_1
    # global count_2
    print(count_3)  # 调用全局变量count_3
    count_1 = count_1 + 1
    count_2 += 1    # 如果函数内部没有global关键字，无法对全局变量重新赋值，除非像count_2那样重新在函数内部定义global
    print(‘count_1=‘, count_1)
    print(‘count_2=‘, count_2)


cc()