判断密码强度
课本案例：

from string import ascii_lowercase,ascii_uppercase,digits

pwd = input("请输入密码：")
flag1 = False;
flag2 = False;
flag3 = False;
flag4 = False;
r = []
d= {1:'弱',2:'适中',3:'高',4:'强'}
if len(pwd) <8:
    print("密码长度不低于8位")
else:
    for i in pwd:
        if not flag1 and i in ascii_uppercase:
            flag1 = True;
            r.append(flag1)

        elif not flag2 and i in ascii_lowercase:
            flag2 = True;
            r.append(flag2)

        elif not flag3 and i in digits:
            flag3 = True;
            r.append(flag3)

        elif not flag4 and i in "+-@#%^&*./!":
            flag4 = True;
            r.append(flag4)
    print(r)
    print("密码强度：", flag1, flag2, flag3, flag4)
    print("密码强度：", d.get(r.count(True),'error'))