Python3 tkinter label value - json

Question

I need some help, I trying to update the etcprice label value after I push the button and after every 5 seconds, in terminal works, but in tk window not. I stucked here :( please, help me.
I tried to setup the "price" to "StringVar()" but in that case I got a lot of errors.
Many thanks
import urllib.request
from urllib.request import *
import json
import six
from tkinter import *
import tkinter as tk
import threading
price = '0'
def timer():
threading.Timer(5.0, timer).start()
currentPrice()
def currentPrice():
url = 'https://api.cryptowat.ch/markets/bitfinex/ethusd/price'
json_obj = urllib.request.urlopen(url)
data = json.load(json_obj)
for item, v in six.iteritems(data['result']):
# print("ETC: $", v)
price = str(v)
# print(type(etcar))
print(price)
return price
def windows():
root = Tk()
root.geometry("500x200")
kryptoname = Label(root, text="ETC price: ")
kryptoname.grid(column=0, row=0)
etcprice = Label(root, textvariable=price)
etcprice.grid(column=1, row=0)
updatebtn = Button(root, text="update", command=timer)
updatebtn.grid(column=0, row=1)
root.mainloop()
windows()
The solution was: I created a new String variable called “b” and I changed the etcprice Label variable to this.
After I added this b.set(price) in currentPrice() def: and is working.

Answer 1

The price variable is a global - if you're trying to change it, you need to do so explicitly:
def currentPrice():
global price
url = 'https://api.cryptowat.ch/markets/bitfinex/ethusd/price'
json_obj = urllib.request.urlopen(url)
data = json.load(json_obj)
for item, v in six.iteritems(data['result']):
# print("ETC: $", v)
price = str(v)
# print(type(etcar))
print(price)
return price
otherwise, Python will 'mirror' it as a local variable inside the function, and not modify the global.
It's not a good idea to keep on launching more and more threads each time you click the button - so:
updatebtn = Button(root, text="update", command=currentPrice)
probably makes more sense.
You don't need to use threads here, just to call functions 'in the background'. You can use tkinter's own .after function instead to delay caling functions. (it uses milliseconds, not float second values, btw)
def timer(delay_ms, root, func):
func()
root.after(delay_ms, timer, root, func)
might be a helpful kind of function.
Then before you launch your mainloop, or whenever you want the getting to start, call it once:
timer(5000, root, currentPrice)
If you want the currentPrice function to run in a separate thread, and so not block your main GUI thread if there is network lag, for instance, then you can use threads more like this:
Thread(target=currentPrice, daemon=True).start()
which will run it in a daemon-thread - which will automatically get killed if you close the program, or ctrl-c it, or whatever. So you could put that line in a getCurrentPriceBG or similar function.