如何删除我在 python 中输入到文本文件中的几行文本？

Question

我正在 python 中制作一个简单的小型密码管理器。我具有创建一个帐户的功能，该帐户具有 3 个输入、用户名、密码和网站。 我有一个 function 可以查看所有帐户，其中显示了所有信息所在的文件 info.txt 的内容。 我试图创建一个 function 来删除一个条目，但我不确定如何让 function 删除与用户名关联的所有信息行。 我想要一个输入询问“要删除哪个帐户”你输入用户名，它会删除 info.txt 中与用户名关联的所有信息

代码：

import os.path #Imports os module using path for file access


def checkExistence(): #Checking for existence of file
    if os.path.exists("info.txt"):
        pass #pass is used as a placeholder bc if no code is ran in an if statement and error comes.
    else:
        file = open("info.txt", "w") #creates file with name of info.txt and W for write access
        file.close()
    

def appendNew():
    #This function will append a new password in the txt file
    file = open("info.txt", "a") #Open info.txt use a for appending IMPORTANT: opening a file with w for write will write over all existing data
    

    userName = input("Enter username: ")
    print(userName)
    os.system('cls')
    password = input("Enter password: ")
    print(password)
    os.system('cls')
    website = input("Enter website: ")
    print(website)
    os.system('cls')

    print()
    print()

    usrnm = "Username: " + userName + "\n" #Makes the variable usrnm have a value of "Username: {our username}" and a new line
    pwd = "Password: " + password + "\n"
    web = "Website: " + website + "\n"

    file.write("----------------------------------\n")
    file.write(usrnm)
    file.write(pwd)
    file.write(web)
    file.write("----------------------------------\n")
    file.write("\n")
    file.close()

def readPasswords():
    file = open("info.txt", "r") #Open info.txt with r for read
    content = file.read() # Content is everything read from file variable (info.txt)
    file.close()
    print(content)





checkExistence()

while True:
    choice = input("Do you want to: \n 1. Add account\n 2. View accounts\n 3. Delete account\n")
    print(choice)
        


    if choice == "1":
        os.system('cls')
        appendNew()
    elif choice == "2":
        os.system('cls')
        readPasswords()
    elif choice == "3":
        os.system('cls')
    else:
        os.system('cls')
        print("huh? thats not an input.. Try again.\n")
    

我尝试通过删除与用户名匹配的行来删除帐户 function。 我唯一的问题是它只删除了 info.txt 中带有用户名的行，但没有删除与该用户名关联的密码和网站。

Answer 1

首先，您使用了错误的工具来解决问题。 pandas是一个不错的尝试库，它使用.csv文件（可以将其视为面向孔隙程序的 excel 文件）。 但是，如果您真的想使用基于文本文件的方法，您的解决方案将如下所示：

with open(textfile, 'r+') as f:
    lines = [line.replace('\n', '') for line in f.readlines()]
    # The above makes a list of all lines in the file without \n char
    index = lines.index(username)
    # Find index of username in these lines
    for i in range(5):
        lines.pop(index)
    # Delete the next five lines - check your 'appendNew' function
    # you're using five lines to write each user's data
    print(lines)
    f.write("\n".join(lines))
    # Finally, write the lines back with the '\n' char we removed in line 2


# Here is your readymade function:

def removeName(username):
    with open("info.txt", 'r+') as f:
        lines = [line.replace('\n', '') for line in f.readlines()]
        try:
            index = lines.index(username)
        except ValueError:
            print("Username not in file!")
            return
        for i in range(5):
        lines.pop(index)
        print(lines)
        f.write("\n".join(lines))


# Function that also asks for username by itself

def removeName_2():
    username = input("Enter username to remove:\t")
    with open("info.txt", 'r+') as f:
        lines = [line.replace('\n', '') for line in f.readlines()]
        try:
            index = lines.index(username)
        except ValueError:
            print("Username not in file!")
            return
        for i in range(5):
        lines.pop(index)
        print(lines)
        f.write("\n".join(lines))


# Usage:
removeName(some_username_variable)
removeName_2()

同样，这是一种相当笨拙且容易出错的方法。 如果您更改了每个用户详细信息的存储格式，则必须更改for循环中删除的行数。 尝试 pandas 和 csv 文件，它们节省了大量时间。

如果您对这些感到不舒服或者您刚刚开始编码，请尝试 json 库和.json文件 - 在高层次上，它们是将数据存储到文件中的简单方法，并且可以使用json库在一个单行代码。 您应该能够在网上找到很多关于 pandas 和 json 的建议。

如果您无法理解 function 的作用，请尝试阅读try-except块和 function 参数（以及可能的全局变量）。