Print Updated Variable using Python Threading

Question

I'm trying to print an updated value and store it in a CSV file. Im using threading and the print would be every 1 second, however after every second that ellapses its the same value that is printed. Can someone help?

import urllib.request, urllib.parse, urllib.error
import json
import threading
import time

localtime = time.asctime( time.localtime(time.time()))



url = 'api'

uh = urllib.request.urlopen(url)
data = uh.read().decode()

js =json.loads(data)


def last_price():
  threading.Timer(1.0, last_price).start()
  print(js['last'])
  print(localtime)


last_price()

Egal · Accepted Answer · 2017-07-31 00:18:59Z

1

The variable js is currently evaluated only once. If you want to query the API every second, move the query code inside the function being executed by the timer:

url = 'api'

def last_price():
    localtime = time.asctime( time.localtime(time.time()))
    uh = urllib.request.urlopen(url)
    data = uh.read().decode()
    js = json.loads(data)
    print(js['last'])
    print(localtime)
    threading.Timer(1.0, last_price).start()

last_price()

answered Jul 31, 2017 at 0:18

Egal

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4 Comments

Arthur Spoon Over a year ago

This is a good way of doing it, but since it takes some time for Python to execute all the code inside the function, it will technically be a bit more than a minute... (which I wouldn't say is an issue)

BorangeOrange1337 Over a year ago

thank you, realized this myself after walking away and thinking about it for a second. Still a noob here...thx!

Egal Over a year ago

@ArthurSpoon you're correct, but if you fire the timer at the beginning you're risking spawning many threads if, for example, the API is unresponsive and blocks you for a long time. Handling that will be an unnecessary overhead if millisecond precision is not of high priority.

Arthur Spoon Over a year ago

I was more making a comment about Thread in general doing that (see this question for example). But as I said, I don't think it's an issue here, I just wanted to make a precision :)

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