Chapter 5 if 语句

检查用户名是否被使用，比较时不区分大小写

current_users = ['Amy', 'Bob', 'Cathy', 'Daisy', 'Ellen']
new_users = ['Amy', 'Bob', 'CATHY', 'DAISY', 'Grey']

current_users_lower = [user.lower() for user in current_users]

for new_user in new_users:
    if new_user.lower() in current_users_lower:
        print("You need make a special name.")
    else:
        print("The name is unused.")

打印列表中数字对应的序数

numbers = ['1', '2', '3', '4', '5', '6', '7', '8', '9']

for number in numbers:
    if number == '1':
        print("1st")
    elif number == '2':
        print("2nd")
    elif number == '3':
        print("3rd")
    else:
        print(number + "th")