如何使用 Tkinter 正确制作 OPEN 和 SAVE 功能？

Question

I am making a simple shopping list application. Whenever I try to save the content from the listbox shopping_list it saves as a tuple ('.., .., ...,') in the .txt file the function creates.

When I use the open button, the listbox displays the text as a tuple .

Example:

If in the entry field I write something like pizza and add it to the listbox and save it. When I try to open the same file into the listbox , the listbox now displays: ('pizza') . How can I get the listbox to display only pizza ?

The code:

from tkinter import *
from tkinter import messagebox
from tkinter import filedialog
from PIL import ImageTk, Image


def add_item():
    '''
        This function takes the input from the entry field
        and places the item in a shopping list.

    :return: Adds to list
    '''

    if len(user_input.get()) == 0: # Checks if user typed into the entry field.
        messagebox.showwarning("Warning", "No keys were detected from the Entry field") # Send warning for no input.

    # Else statement for adding the user input to shopping list.
    else:
        shopping_list.insert(END, user_input.get())
        user_input.delete(0, END)  # Deletes whatever the user wrote in the entry box after button is clicked.


def remove_item():
    '''
        This function deletes the selected items when REMOVE button is clicked
    '''
    try:
        selected = shopping_list.curselection()
        for item in selected[::-1]:  # Fetches all selected items from shopping list
            shopping_list.delete(item)


    # Make a warning if the shopping list is empty or items are not selected when REMOVE button is clicked.
    except TclError:
        messagebox.showwarning("Warning", "The shopping list is either empty \nor you didn't select an item")


def open_list():
    '''
        This function opens an existing shopping list that was previously saved.
    :return: Opens older saved files.
    '''
    root.file = filedialog.askopenfilename(initialdir="./", title="Select a file",
                                           filetypes=(("Txt files", "*.txt"), ("All files", "*,*")))

    with open(root.file, "r") as file:
        data_content = file.read()
        shopping_list.delete(0, END)
        shopping_list.insert(END, data_content)


def save_file():
    '''
        This function saves the whole shopping list and writes the content to the "shopping_list.txt" file.
    :return: None
    '''
    text_file = filedialog.asksaveasfilename(defaultextension=".txt")
    try:
        with open(text_file, "w") as file:
            file.write(str(shopping_list.get(0, END)))
    except FileNotFoundError:
        messagebox.showinfo("Alert", "No file was saved")

# backup eldre løsning:
"""
def save_file():
    '''
        This function saves the whole shopping list and writes the content to the "shopping_list.txt" file.
    :return: None
    '''
    root.filename = filedialog.asksaveasfilename()
    with open("shopping_list.txt", "w") as f:
        for i in shopping_list.get(0, END):
            f.write(i+"\n")

"""



# Root files
root = Tk()
root.title("Skoleoppgave OBLIG 5")
root.iconbitmap('favicon.icns')
root.geometry("500x500")
root.resizable(0, 0)


# TODO: Entry  widget  ENTRY  1
# Creating an Entry widget so user can add items to shopping-list.
user_input = Entry(root, relief=SUNKEN)
user_input.pack()
user_input.place(x=250, y=20, anchor=N)


# Todo: Buttons widget ADD ITEM 2
# Make a Button-widget that adds the user input from entry field to the shopping list.
add_entry = Button(root, text="ADD ITEM", command=add_item, padx=10, pady=5)
add_entry.pack()
add_entry.place(x=158, y=57)



# Todo: Listbox  widget 4
# Creating Listbox for shopping list items
shopping_list = Listbox(root, selectmode=EXTENDED)
shopping_list.pack()
shopping_list.place(x=160, y=100)

"""
# Opens last saved shopping list when program starts.
try:
    read = open("shopping_list.txt","r")
    list_file = read.readlines()
    read.close()
    for data in list_file:
        shopping_list.insert(0, END, data)
except FileNotFoundError:
    read = open("shopping_list.txt","w")
"""


# Todo: Buttons widget REMOVE 3
# Make a Button-widget that deletes the selected item from shopping list
remove_entry = Button(root, text="REMOVE", command=remove_item, padx=10, pady=5)
remove_entry.pack()
remove_entry.place(x=160, y=285)


# Todo: Buttons widget OPEN 5
# Make a Button-widget that deletes the selected item from shopping list
open_file = Button(root, text="OPEN", command=open_list, padx=10, pady=5)
open_file.pack()
open_file.place(x=160, y=285)

# Todo: Buttons widget SAVE 6
# Make a Button-widget that deletes the selected item from shopping list
save_file = Button(root, text="SAVE", command=save_file, padx=10, pady=5)
save_file.pack()
save_file.place(x=282, y=57)

root.mainloop()

Answer 1

As mentioned in the comments, you are trying to put a string into a method that is asking for a tuple, that will give an error.

so one way is that you add functionality both in reading and writing to write a data format to the file that you control yourself. tip is trying to replicate one to one what you see in the listbox to the textfile. It looks like your "eldre losning" will put one item per line. So the thing is to read the file so that you get a list of strings where every row becomes an item in the list. Hint... .split on strings works good for that.

Or, just deal with the string you already have in the file. One way to do that is to add/modify the following.

from ast import literal_eval # added import for safe evals

# modified open
with open(root.file, "rt") as file:
    data_content = literal_eval(file.read())
    shopping_list.delete(0, END)
    shopping_list.insert(END, *data_content)

Side note #1, you don't need .pack() if you use .place . Side note #2, next time around, mention that you are doing homework upfront. Side note #3, if you use what's in this answer - you might have to do some reading before you can explain why it could be done like this to be believed that you came up with it yourself :-)

Good luck with your studies and learning.