用Switch编写，输入年份月份输出天数

year = int(input("请输入年份："))
month = int(input("请输入月份："))

days = 0

if month in [1, 3, 5, 7, 8, 10, 12]:
    days = 31
elif month in [4, 6, 9, 11]:
    days = 30
else:
    if year % 4 == 0 and year % 100 != 0 or year % 400 == 0:
        days = 29
    else:
        days = 28

print("{}年{}月的天数为：{}".format(year, month, days))

使用Switch语句替代if-elif语句：

year = int(input("请输入年份："))
month = int(input("请输入月份："))

days = 0

switcher = {
    1: 31,
    2: 28 if year % 4 != 0 or year % 100 == 0 and year % 400 != 0 else 29,
    3: 31,
    4: 30,
    5: 31,
    6: 30,
    7: 31,
    8: 31,
    9: 30,
    10: 31,
    11: 30,
    12: 31
}

days = switcher.get(month, "Invalid month")

print("{}年{}月的天数为：{}".format(year, month, days))