用列表实现一个简单的图书管理系统 python

#coding=utf-8

book_list=[]  #图书馆所有书

unborrowed_book=[]  #可借阅的书

borrowed_book=[]  #已经借出去的书

def add():  #添加书

    global book_list

    global unborrowed_book

    book_name=raw_input(u"请输入要添加的书名：".encode("gbk"))

    book_list.append(book_name)

    unborrowed_book.append(book_name)

    print u"添加书成功"

def borrow_book():  #借书

    global unborrowed_book

    global borrowed_book

    while 1:

        book_name=raw_input(u"请输入要借的书名：".encode("gbk"))

        if book_name in unborrowed_book:

            unborrowed_book.remove(book_name)        

            borrowed_book.append(book_name)

            print u"借书成功"

            break

        else:

            print u"抱歉，您要借的书不存在!"

            continue_back=raw_input(u"继续借书请输入：c 返回主菜单请输入：b ：".encode("gbk"))

            if continue_back.lower()=="c":

                continue

            elif continue_back.lower()=="b":

                break

            else:

                print u"输入数据无效"            

def return_book():  #还书

    global borrowed_book

    global unborrowed_book

    while 1:

        book_name=raw_input(u"请输入要还的书名：".encode("gbk"))

        if book_name in borrowed_book:

            borrowed_book.remove(book_name)

            unborrowed_book.append(book_name)

            print u"还书成功"

            break

        else:

            print u"您输入的书名不是此图书馆的"

            continue_back=raw_input(u"继续还书请输入：c 返回主菜单请输入：b ：".encode("gbk"))

            if continue_back.lower()=="c":

                continue

            elif continue_back.lower()=="b":

                break

            else:

                print u"输入数据无效"    

menu_info='''

添加书--请输入：1

借书--请输入：2

查看可借阅的书--请输入：3

查看借出去的书--请输入：4

还书--请输入：5

查看所有书--请输入：6

退出--请输入：q

'''

import sys

print menu_info.decode("utf-8")

while True:    

    command=raw_input(u"请输入您要做的操作选项：".encode("gbk"))

    if command=="1":

        add()

    elif command=="2":

        borrow_book()

    elif command=="3":

        if unborrowed_book==[]:

            print u"抱歉，没有可以借的书了!"

        else:

            print u"可借阅的书：",unborrowed_book    

    elif command=="4":

        if borrowed_book==[]:

            print u"没有借出去的书！"

        else:

            print u"借出去的书：",borrowed_book

    elif command=="5":

        return_book()

    elif command=="6":

        if book_list==[]:

            print u"图书馆还没有书，赶快去添加吧！"

        else:

            print u"图书馆所有的书：",book_list

    elif command=="q":

        sys.exit()

    else:

        print u"输入数据无效！"