import sys,shelve

def enter_cmd():
    cmd = input(‘Please enter the cmd(? for help): ‘)
    cmd = cmd.strip().lower()

    return cmd

def print_help():
    ‘存储（增加）、查找、更新（修改）、循环打印、删除、退出、帮助‘
    print(‘The available commons are: ‘)
    print(‘quit     : Save changes and exit‘)
    print(‘?        : Print this message‘)


def main():
    database = shelve.open(‘database20210915001.dat‘, writeback=True)
    try:
        while True:
            cmd = enter_cmd()
            if cmd == ‘?‘:
                print_help()
            elif cmd == ‘coordinate‘:
                enter_coordinate()
            elif cmd == ‘quit‘:
                return
    finally:
        database.close()

if __name__==‘__main__‘:
  main()