如何使用 for 循环在 tkinter 中用空白框填充屏幕设计的 rest？

Question

I am trying to make a shopping-inspired vending machine UI. The goal is to fill up my frame with frames using for loop and 2D list, then pack on buttons and labels onto it. Codes are as followed:

    frames = []
    frame_order = []
    num = 0

    for x in range(5):
        frames.append([])
        for y in range(5):
            frames[x].append(5)

    for x in range(5):
        for y in range(5):
            frames[x][y] = Frame(store_canvas, width=1520 / 5, height=1030 / 5, bd = 2, relief = SOLID)
            frames[x][y].grid(row=y, column=x)
            frames[x][y].pack_propagate(False)
            frame_order.append(frames[x][y])

This will reun an SQL query database that will return with an item list as a list[] .Then fill up the frames inside the 2D list

retrieve_tiem() 

I have also set up another frame on the side that has other filters. the problem is that if the filter query SQL and returns with an item list less than the grid size (5x5, a total of 25 items) then the for loop won't run as it cannot populate. to avoid this, I tried to use Try and Except but the loop would just fill the remaining space with buttons instead.

for frame in frame_order:
    try:
        Button(frame, anchor='nw', height = 9, width = 35, font = 20).pack()
        Label(frame, text=str(Item_list[num]), anchor='nw', font = 20, width = 35, bg = 'darkgreen', fg = 'yellow' ).pack()
        num += 1
    except:
        pass

Is there a way to avoid this? Like not creating the button when the Item list run out off item or fill the rest of the list with '*blank*' until the list reach the total amount of item that the frame can hold? I am also open to other methods too if it works. All answer are appreciated, please go easy on me as I am still learning python and SQL:)

Answer 1

The problem is with your try statement. Here's an example:

a = 5
try:
    a += 7
    int("str") #This is just to raise an exception
except:
    pass

After running this code, the value of a will be 12, even though an error occured. This is the same thing that is happening in your code. The line that creates the button is run successfully, but the creating the label raises an exception. This is why you get buttons in the remaining space. This can be resolved using else . If we try this instead:

a = 5
try:
    int("str") #This is just to raise an exception
except:
    pass
else:
    a += 7

The a += 7 line will only be run if there is not exception in the try statement, so the value will remain 5. For your code, this will be

try:
    Item_list[num] #This is what causes the error
except:
    pass
else:
    Button(frame, anchor='nw', height = 9, width = 35, font = 20).pack()
    Label(frame, text=str(Item_list[num]), anchor='nw', font = 20, width = 35, bg = 'darkgreen', fg = 'yellow' ).pack()
    num += 1

Alternatively, you could have an if statement to check if num is larger than the length of the data returned, but there's not enough information in the question for me to be sure that will work.

Answer 2

You can actually use 1-D list instead of 2-D list. Below is an example based on your code:

from tkinter import *
import random

root = Tk()

store_canvas = Frame(root)
store_canvas.pack()

# create the 25 frames
ROWS = COLS = 5
MAX_ITEMS = ROWS * COLS
frames = []
for i in range(MAX_ITEMS):
    frames.append(Frame(store_canvas, width=1520/COLS, height=1030/ROWS, bd=2, relief=SOLID))
    frames[-1].grid(row=i//COLS, column=i%COLS)
    frames[-1].pack_propagate(False)

# function to simulate retrieving data from database table
def retrieve_tiem():
    return [f"Item #{i+1}" for i in range(random.randint(1,MAX_ITEMS))]

# function to show the retrieved items
def update_list():
    Item_list = retrieve_tiem()
    label_font = ("Arial", 20)
    for i, frame in enumerate(frames):
        for w in frame.winfo_children():
            w.destroy()
        if i < len(Item_list):
            item = Item_list[i]
            Button(frame).pack(fill="both", expand=1)
            Label(frame, text=item, font=label_font, bg="darkgreen", fg="yellow").pack(fill="x")

update_list()
root.bind("<F5>", lambda e: update_list())
root.mainloop()