Python 如何从while循环更改条件

我正在尝试创建一个阅读列表，使用两个函数-一个用于添加书籍，另一个用于显示书籍。添加书籍功能需要执行，直到用户确认更新完成。代码如下：

book_list = []

def add_books(books):
    book_record = {}
    completed = "no"
    while completed == "no":
        title = input("Enter title : ")
        author = input("Enter author : ")
        year = input("Enter year of publication : ")
        book_record.update({"title": title, "author": author, "year_publ": year})
        books.append(book_record)
        print(books)
        completed = input("update completed ? yes/no")
    return books


def display_books(books):
    for book in books:
        title = book["title"]
        author = book["author"]
        year = book["year_publ"]
        print(f"{title}, {author}, {year}")


option = input("Enter 'a' to add and 'd' to display the books or 'q' to quit :")

while option != "q" :
    if option == "a":
        book_list = add_books(book_list)
    elif option == "d":
        display_books(book_list)
    else:
        print("Invalid Option")
        option = input("Enter 'a' to add and 'd' to display the books or 'q' to quit :")

当我执行这段代码时，While循环忽略已完成的条件，并不断请求添加更多书籍，即使用户确认更新已完成

怎么了？我知道我正在尝试更新循环中已完成的内容，这可能就是原因。有哪些选择

谢谢你的帮助

谢谢和问候

---

Sachin

您的代码一直在询问，因为在

添加书籍

完成后，

选项

仍然是

“a”

，并且您的“主”循环没有从用户处获得

选项

的新值

始终将“是否继续？”问题作为循环的一部分

对于这类任务，我建议使用带条件中断的无止境循环（

，True:

）。（在我看来）更容易理解：

这样-我添加了一个helper函数

input_letter

，它返回用户响应中经过修剪的小写首字母，以便以后更容易管理）：

你试过这个吗

def add_books(books):
book_record = {}
completed = "no"
while True:
    title = input("Enter title : ")
    author = input("Enter author : ")
    year = input("Enter year of publication : ")
    book_record.update({"title": title, "author": author, "year_publ": year})
    books.append(book_record)
    print(books)
    completed = input("update completed ? yes/no")
    if completed == 'yes':
        break
return books

---

因此，问题在于

选项=input（“输入'a'添加书籍，输入'd'显示书籍，或输入'q'退出：”）

。你只要求一次选择，你需要的是一个无休止的循环，继续要求新的选择。在您的方法中，当“用户”选择“a”选项时，他/她再也不会被询问，因此选项仍保留在“a”上，因此

add\u books（）

函数将无休止地运行

您应将最后一部分更改为：

为True时：
选项=输入（“输入'a'以添加，输入'd'以显示书籍，或输入'q'以退出：”）
如果选项==“a”：
图书列表=添加图书（图书列表）
elif选项==“d”：
显示书籍（书籍列表）
elif选项==“q”：
退出
其他：
打印（“无效选项”）

如果您不想保留ypur代码，请使用： 另一个条件是告诉循环已完成的已更新并退出

book_list = []

def add_books(books):
    book_record = {}
    completed = "no"
    while completed == "no":
        title = input("Enter title : ")
        author = input("Enter author : ")
        year = input("Enter year of publication : ")
        book_record.update({"title": title, "author": author, "year_publ": year})
        books.append(book_record)
        print(books)
        completed = input("update completed ? yes/no")

        if completed == "yes":
            completed = completed
            break
    return books


def display_books(books):
    for book in books:
        title = book["title"]
        author = book["author"]
        year = book["year_publ"]
        print(f"{title}, {author}, {year}")


option = input("Enter 'a' to add and 'd' to display the books or 'q' to quit :")

while option != "q" :
    if option == "a":
        book_list = add_books(book_list)
    elif option == "d":
        display_books(book_list)
    else:
        print("Invalid Option")
    option = input("Enter 'a' to add and 'd' to display the books or 'q' to quit :")

---

当我执行这段代码时，While循环忽略已完成的条件，并不断请求添加更多书籍，即使用户确认更新已完成。这对我来说似乎很好，你做过调试吗？别忘了对帮助你的答案进行投票，当你的问题解决后，从中选出一个被接受的答案。

book_list = []

def add_books(books):
    book_record = {}
    completed = "no"
    while completed == "no":
        title = input("Enter title : ")
        author = input("Enter author : ")
        year = input("Enter year of publication : ")
        book_record.update({"title": title, "author": author, "year_publ": year})
        books.append(book_record)
        print(books)
        completed = input("update completed ? yes/no")

        if completed == "yes":
            completed = completed
            break
    return books


def display_books(books):
    for book in books:
        title = book["title"]
        author = book["author"]
        year = book["year_publ"]
        print(f"{title}, {author}, {year}")


option = input("Enter 'a' to add and 'd' to display the books or 'q' to quit :")

while option != "q" :
    if option == "a":
        book_list = add_books(book_list)
    elif option == "d":
        display_books(book_list)
    else:
        print("Invalid Option")
    option = input("Enter 'a' to add and 'd' to display the books or 'q' to quit :")