why the thread runs only once? - python-3.x

Question

This is my client:
from tkinter import *
import tkinter.simpledialog
import socket
import select
import ssl
import threading
Host = '127.0.0.1'
Port = 87
def create_connection():
return socket.create_connection((Host, Port))
def gui():
global e1
global txt
root = Tk()
root.title('Amifre chat')
root.geometry("700x515")
txt = Text(root, width=70, height=30)
txt.config(state=DISABLED)
e1 = Entry(root, width=93)
e1.place(x=0, y=487)
txt.place(x=0)
t = threading.Thread(target=display_msg())
t.daemon = True
root.after(1, t.start())
root.mainloop()
def display_msg():
r, w, x = select.select([client_socket], [], [], 0.00001)
if client_socket in r:
data = client_socket.recv().decode()
txt.config(state=NORMAL)
txt.insert(INSERT, data + '\n')
txt.config(state=DISABLED)
if __name__ == '__main__':
start = Tk()
b = Button(start, text='Click to join the chat', command=create_user_name).grid(row=0)
context = ssl.create_default_context(ssl.Purpose.CLIENT_AUTH)
client_socket = create_connection()
client_socket = context.wrap_socket(client_socket, server_hostname='127.0.0.1')
start.mainloop()
gui()
This is a client for chat and the thread in the gui function call the display_msg function only once so does anyone have any idea why is it? (sending data works well and it dislplayed in client without GUI)

Answer 1

You should pass only the function name to target option, and call t.start() directly without using after():
t = threading.Thread(target=display_msg, daemon=True)
t.start()
Then, you need to use while loop inside display_msg() to keep receiving data from server:
def display_msg():
while True:
r, w, x = select.select([client_socket], [], [])
if client_socket in r:
data = client_socket.recv(1024).decode()
txt.config(state=NORMAL)
txt.insert(INSERT, data + '\n')
txt.config(state=DISABLED)

Answer 2

This code:
t = threading.Thread(target=display_msg())
is functionally identical to this code:
result = display_msg()
t = threading.Thread(result)
And this code:
root.after(1, t.start())
is functionally identical to this code:
result = t.start()
root.after(1, result)
In both threading.Thread and after, the values given to the functions must be references to a function rather than the result of a function (unless the result is itself a reference to a function).
t = threading.Thread(target=display_msg)
...
root.after(1, t.start)
Regardless, the answer to "why the thread runs only once?" is because that's what threads do. Threads run until they are done. If you need code to run in a loop, you will need to write the loop yourself.