输入星期几的第一个字母来判断一下是星期几，如果第一个字母一样，则继续判断第二个字母。

def day_of_week():
    s1 = input("please input the first letter:")
    week = ['Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday', 'Saturday', 'Sunday']
    lst = [x for x in week if x.lower().startswith(s1.lower())]
    while len(lst) > 1:
        s = input("please input the next letter:")
        s1 += s
        lst = [x for x in week if x.lower().startswith(s1.lower())]

    if not lst:
        print('please input the right letter!')
        dow = day_of_week()
        lst = [dow]
    return lst[0]


if __name__ == '__main__':
    print(day_of_week())

#!/usr/bin/python
# -*- coding: UTF-8 -*-

letter = raw_input("please input:")
#while letter  != 'Y':
if letter == 'S':
    print ('please input second letter:')
    letter = raw_input("please input:")
    if letter == 'a':
        print ('Saturday')
    elif letter  == 'u':
        print ('Sunday')
    else:
        print ('data error')
   
elif letter == 'F':
    print ('Friday')
   
elif letter == 'M':
    print ('Monday')
   
elif letter == 'T':
    print ('please input second letter')
    letter = raw_input("please input:")
 
    if letter  == 'u':
        print ('Tuesday')
    elif letter  == 'h':
        print ('Thursday')
    else:
        print ('data error')
       
elif letter == 'W':
    print ('Wednesday')
else:
    print ('data error')

以上实例输出结果为：

please input:S
please input second letter:
please input:a
Saturday