range的使用：注意，在python3中，交互模式下已经不显示了

for循环的使用

打印50-70

# 第一种方案for i in range(100):    if i <= 70 and i >= 45:   #注意这里使用的是 and/or/not  非java中的&&，||,!        print (i)# 第二种方案for i in range(50,71):    print (i)

break/continue的使用

exit_Flag = Falsefor i in range(100):    if i < 5:        continue    print("L_1:",i)    for j in range(10):        print("layer2:",j)        if j == 7:            exit_Flag=True            break    if exit_Flag:        break

用户登录小程序

_user="hhh"_pass="hello"count = 1while count <= 3:    username = input("Please input the username:")    password = input("Please input the password:")    if _pass == password and _user == username:        print("Welcome to BBT,", username)        break    else:        print()        print("Invalid username or password,you still have " + str(3 - count) + " times")    count += 1else:    print("Time out,~-~")