python字典实现一个记事本

from time import sleep, strftime

user = "Cytus"
calendar = {}


def welcome():
    print "Welcome to use this calendar. %s" % user
    print "Calendar is opening."
    sleep(1)
    print strftime("%A %B %d %Y")
    print strftime("%H:%M:%S")
    sleep(1)
    print "What would you like to do?"


def start_calendar():
    welcome()
    start = True
    while start:
        user_choice = raw_input("A to add, U to Update, V to View, D to Delete, X to Exit: ")
        user_choice = user_choice.upper()
        if user_choice == "V":
            if len(calendar.keys()) < 1:
                print "The calendar is empty."
            else:
                print calendar
        elif user_choice == "U":
            date = raw_input("What date? ")
            update = raw_input("Enter the update: ")
            calendar[date] = update
            print "Update successful."
            print calendar
        elif user_choice == "A":
            event = raw_input("Enter event: ")
            date = raw_input("Enter date (MM/DD/YYYY): ")
            if (len(date) > 10) or int(date[6:]) < int(strftime("%Y")):
                print "invaild date."
                try_again = raw_input("Try again? Y for yes, N for No: ")
                try_again = try_again.upper()
                if try_again == "Y":
                    continue
                else:
                    start = False
            else:
                calendar[date] = event
                print "Successfully added."
                print calendar
        elif user_choice == "D":
            if len(calendar.keys()) < 1:
                print "The calendar is empty."
            else:
                event = raw_input("What event? ")
                for date in calendar.keys():
                    if calendar[date] == event:
                        del calendar[date]
                        print "Delete successfully."
                        print calendar
                    else:
                        print "incorrect event was specified."
        elif user_choice == "X":
            start = False
        else:
            print "invalid input."
            start = False


start_calendar()