Why are there two different results if I debug or run it?

Question

I make a simple function to load a web photo in tkinter. When it is crawling a photo,the GUI will show a tip "loading...".

When it finishes,then the photo will cover this tip. For avoiding GUI freezing when it is crawling,I use threading module to do this.

Here is a Minimal, Reproducible Example.

import requests
import threading
import tkinter
from PIL import ImageTk,Image
from io import BytesIO

class MultiProcessGetResultWithoutArgs(threading.Thread): # get thread result
    def __init__(self, func):
        threading.Thread.__init__(self)
        self.func = func
        self.result = None

    def getResult(self):
        return self.result

    def run(self):
        self.result = self.func()

def GetOne():
    return Image.open(BytesIO(requests.get('https://s2.ax1x.com/2020/02/07/12usP0.th.jpg').content))

def checkWhetherGet(): # judge whether it has result.
    result = thread.getResult()
    if result:
        img1 = ImageTk.PhotoImage(result)
        tkinter.Label(w,image=img1).grid(row=0,column=0)
        w.update()
        w.after_cancel(1)
    else:
        w.after(100,checkWhetherGet)

def about():
    global w,thread
    w = tkinter.Toplevel()
    tkinter.Label(w,text="loading....").grid(row=0,column=0)
    thread = MultiProcessGetResultWithoutArgs(GetOne)
    thread.start() # non-block thread
    w.after(1000,checkWhetherGet)
    w.mainloop()

Win = tkinter.Tk()
tkinter.Button(Win,text="start",command=about).grid()
Win.mainloop()

Now if I debug this code,it can show the image. But if I run this code,it will only enlarge the window size but not show the image.

Answer 1

Finally I find my problem.Like this said,I keep reference. xx.image = img1 And solve my problem.But what really makes me confused is that why debugger won't use garbage collection.