tkinter: RuntimeError: threads can only be started once

Question

but I'm trying to make the GUI for my script, when I click bt_send I start a thread (thread_enviar), that thread also start other thread (core), the problem is that thread_enviar is running for ever so I got this error when I try to click bt_send again:

File "/anaconda3/envs/tensor/lib/python3.6/threading.py", line 842, in start raise RuntimeError("threads can only be started once") RuntimeError: threads can only be started once

My code:

import tkinter as tk
from tkinter import filedialog
import pandas as pd
from tkinter import messagebox
from tkinter import ttk

import threading
import rnn10forecasting as rnn10f



filepath = ""
model = ""

'''def change_menu(selection):
    global model
    selected = selection
    print(selected)
    model = selected'''



def click():
    global filepath
    print("click")
    filepath = filedialog.askopenfilename(initialdir = "/",title = "Select file",filetypes = (("data files","*.csv"),("all files","*.*")))
    print(filepath)
    label_filepath.config(text = filepath)




def enviar():


    print(filepath)
    try:
        data = pd.read_csv(filepath)

    except:
        messagebox.showerror("Error", "Archivo .csv vacio o formato incompatible")


    if any(data.columns.values != ['date','close','volume','open','high','low']):
        messagebox.showerror("Error", "El archivo .csv no contiene la estructura requerida: [date,close,volume,open,high,low]")




    elif len(data) < 300:
        print("# registros")
        print(len(data))
        messagebox.showerror("Error", "El archivo de be contener como minimo 700 registros")



    else:

        pg_bar.start(500)
        core = threading.Thread(target=rnn10f.forecasting, args=(filepath,))
        #core.daemon = True
        core.start()
        core.join()
        print("VIVO?")
        print(core.isAlive())
        pg_bar.stop()



    return print(thread_enviar.is_alive())



thread_enviar = threading.Thread(target=enviar, args=())


window = tk.Tk()

window.resizable(width=False, height=False)

window.title("LSTM Module")

window.geometry("600x150")


title = tk.Label(text="StockForecaster", font=("Times New Roman", 30))
title.place(relx=0.1, rely=0.05, relwidth=0.8, relheight=0.25)


bt_select = tk.Button(text="Select File", bg="blue", command= click)
bt_select.place(relx=0.7, rely=0.4, relwidth=0.25, relheight=0.2)


label_filepath = tk.Label(text="Please select a .csv File")
label_filepath.place(relx=0, rely=0.4, relwidth=0.7, relheight=0.15)


options = tk.StringVar()



bt_send = tk.Button(text="Send", bg="blue", command=thread_enviar.start)
bt_send.place(relx=0.70, rely=0.7, relwidth=0.25, relheight=0.20)


pg_bar = ttk.Progressbar(window, orient= tk.HORIZONTAL, mode="indeterminate", )
pg_bar.place(relx=0.10, rely=0.75, relwidth=0.55, relheight=0.05)


window.mainloop()

I don' know if there is any way to kill that thread or If I'm doing something wrong.

Answer 1

Question: RuntimeError: threads can only be started once

As I understand, you don't want to run multiple threads, you only want to do a Task in a thread to avoid freezing the Tk().mainloop().
To inhibit, to start a new thread while the previous thread are still running you have to disable the Button or verify if the previous thread is still .alive().

Try the following approach:

import tkinter as tk
import threading, time

class Task(threading.Thread):
    def __init__(self, master, task):
        threading.Thread.__init__(self, target=task, args=(master,))

        if not hasattr(master, 'thread_enviar') or not master.thread_enviar.is_alive():
            master.thread_enviar = self
            self.start()

def enviar(master):
    # Simulating conditions
    if 0:
        pass
    #if any(...
    #elif len(data) < 300:
    else:
        #master.pg_bar.start(500)

        # Simulate long run
        time.sleep(10)
        #rnn10f.forecasting(filepath)

        print("VIVO?")
        #master.pg_bar.stop()

class App(tk.Tk):
    def __init__(self):
        super().__init__()

        bt_send = tk.Button(text="Send", bg="blue", 
                            command=lambda :Task(self, enviar))

if __name__ == "__main__":
    App().mainloop()