如何检查文本文件中的一行文本？

Question

我没有收到任何错误，但它似乎没有检查我的文件中的文本，因为它会附加您输入的任何内容。有人可以帮忙吗？

guest_name = input("What is your name: ")
with open("guests.txt", "a+") as guests_txt:

    names = guests_txt.readlines()


    def find_name():
        if guest_name.lower() in names:
            print("Your name is already taken.")
            name_taken = True
            return name_taken

    name_taken_function = find_name()

    if not name_taken_function:
        guests_txt.write(f"{guest_name.lower()}\n")

Answer 1

模式a+打开文件是追加的，所以打开的时候，当前位置在文件末尾。 readlines() returns 一个空列表。

你应该在阅读它之前guests_txt.seek(0)。

Answer 2

它不起作用的原因是因为.readlines()方法没有去掉多余的'\n'，所以用户输入的名字永远不会等于现有的那些。请改用 .read().splitlines()。另外，尝试打开文件两次，一次以读取模式，然后以追加模式：

guest_name = input("What is your name: ")

with open("guests.txt", "r") as guests_txt:
    name_taken = False
    names = guests_txt.read().splitlines()
    if guest_name.lower() in names:
        if guest_name.lower() in names:
            print("Your name is already taken.")
            name_taken = True

with open("guests.txt", "a") as guests_txt:
    if not name_taken:
        guests_txt.write(f"\n{guest_name.lower()}")

Answer 3

当您使用 a+ 打开文件时，位置设置为最后一个字符。当您尝试阅读它时，由于最后一个字符之后没有其他内容，您将得到一个空文本。

使用guests_txt.seek(0)查找到开头，然后阅读。
另一个问题是，.readlines() 不会删除 \n 字符。相反，您可以使用 .read().splitlines() 来获取没有换行符的行：

guest_name = input("What is your name: ")
with open("guests.txt", "a+") as guests_txt:

    guests_txt.seek(0)
    names = guests_txt.read().splitlines()

    def find_name():
        if guest_name.lower() in names:
            print("Your name is already taken.")
            name_taken = True
            return name_taken

    name_taken_function = find_name()

    if not name_taken_function:
        guests_txt.write(f"{guest_name.lower()}\n")

Answer 4

你可以比许多其他答案更简单地实现这一点。

guest_name = input("What is your name: ")
with open("guests.txt", "a+") as guest_txt:
    guest_txt.seek(0)
    names = guest_txt.read().splitlines()
    if guest_name.lower() in names:
        print(f"Sorry, {guest_name}, your name is already taken.")
    else:
        guest_txt.write(f"{guest_name.lower()}\n")
        print(f"Thanks, {guest_name}, your name has been recorded.")

Answer 5

要添加新名称，您可以使用 guests_file.seek(0, io.SEEK_END)。我还建议简化代码并改进名称：

guest_name = input("What is your name: ").lower()
with open("guests.txt", "a+") as guests_file:
    guests_file.seek(0)
    names = guests_file.readlines()

    def name_is_taken():
        if guest_name + '\n' in names:
            print("Your name is already taken.")
            return True

    if not name_is_taken():
        guests_file.write(f"{guest_name}\n")

如何检查文本文件中的一行文本？

How do you check for a line of text in text files?

python

text-files

python-3.x