Python待办事项应用添加功能异常：新增项未正确显示

问题描述 #

开发Python待办事项应用时，执行add 内容命令添加新待办项后，使用show命令查看列表，发现新增的待办项并未单独显示，而是与列表最后一项内容拼接在一起。

应用代码 #

while True:
    user_action = input("type add, show, edit, remove or exit ")
    user_action = user_action.strip()

    if 'add' in user_action:
        todo = user_action[4:]

        with open('todos.txt', 'r') as file:
            todos = file.readlines()

        todos.append(todo)

        with open('todos.txt', 'w') as file :
            file.writelines(todos)

    elif 'show' in user_action:
        with open('todos.txt', 'r') as file :
            todos = file.readlines()

        for index, items in enumerate(todos):
            items  = items.strip("\n")
            index = index + 1
            row = f"{index}-{items}"
            print(row)

    elif 'edit' in user_action:
        number = int(user_action[5:])
        print(number)
        number = number - 1

        with open('todos.txt', 'r') as file:
            todos = file.readlines()

        new_todo = input("Type the new todo:")
        todos[number] = new_todo + "\n"

        with open('todos.txt', 'w') as file :
            file.writelines(todos)

    elif 'remove' in user_action:
        number = int(user_action[6:])
        with open('todos.txt', 'r') as file:
            todos = file.readlines()
        index = number - 1
        todo_to_remove = todos[index].strip("\n")
        todos.pop(index)
        with open('todos.txt', 'w') as file :
            file.writelines(todos)
        message = f"todo {todo_to_remove} was removed from the list"
        print(message)

    elif 'exit' in user_action:
        break
    else:
        print("Command is not valid ")

print("bye!")

实际操作及输出 #

type add, show, edit, remove or exit add bro
type add, show, edit, remove or exit show
1-ab
2-cd
3-hihellohikrrish
4-hi
5-
6-hiibro
type add, show, edit, remove or exit add broski
type add, show, edit, remove or exit show
1-ab
2-cd
3-hihellohikrrish
4-hi
5-
6-hiibrobroski

期望输出 #

1-ab
2-cd
3-hihellohikrrish
4-hi
5-
6-hii
7-bro
8-broski

问题原因 #

使用readlines()读取文件时，每一行内容会保留末尾的换行符\n，但添加新待办项时，直接将用户输入的内容（无换行符）追加到列表中。写入文件时，新内容会直接拼接在最后一行的末尾，而非单独成一行。

修复方案 #

在添加待办项时，给用户输入的内容加上换行符\n，确保每个待办项在文件中都是单独一行。修改add分支中的代码：

将：

todos.append(todo)

改为：

todos.append(todo + "\n")

修复后验证 #

执行add bro和add broski后，使用show命令会得到符合预期的输出：新增的bro和broski会作为单独的列表项显示，不会与之前的内容拼接。

内容的提问来源于stack exchange，提问作者Krrish