When to call thread.join in a GUI application

Question

import wx
import json
import queue
from collections import namedtuple
import threading


class MyDialog(wx.Frame):

    def __init__(self, parent, title):
        self.no_resize = wx.DEFAULT_FRAME_STYLE & ~ (wx.RESIZE_BORDER | wx.MAXIMIZE_BOX)
        wx.Frame.__init__(self, parent, title=title, size=(500, 450),style = self.no_resize)

        self.panel = wx.Panel(self, size=(250, 270))
        self.emp_selection = wx.ComboBox(self.panel, -1, pos=(40, 50), size=(200,100))
        self.start_read_thread()

        #code to load other GUI components             

        self.Centre()
        self.Show(True)


    def read_employees(self, read_file):
        list_of_emails = queue.Queue()
        with open(read_file) as f_obj:
            employees = json.load(f_obj)
        list_of_emails = [empEmail for empEmail in employees.keys()]
        wx.CallAfter(self.emp_selection.Append, list_of_emails)

    def start_read_thread(self):
        filename = 'employee.json'
        empThread = threading.Thread(target=self.read_employees, args=(filename,))
        empThread.start()

I have a GUI application that loads a combobox, and starts a thread to read some data and load it into the combobox. I don't want the read to block, so that the other GUI components can load.

After calling thread.start() when is it appropriate to call thread.join()? From my understanding, join() waits for the thread to complete, I don't want that, I want to start the thread and allow all the other components to load. Is it bad practice not to call join()

Answer 1

It is perfectly ok to not call join() if you don't need its functionality to wait for the thread to finish.

By the way: In the main thread of a GUI application (the thread automatically created at start in which all GUI things happen) it is bad practice to call any function that sleeps or waits for anything as the GUI doesn't react (freezes) while waiting.