Python Threading timer with package

Question

I've been reading up on threading and tried implementing it into my code however I'm not sure if the way I'm doing it, is the best practise.

My code simply imports a self scripted package which pulls weather data and runs the package every 60 seconds thereafter.

I plan on running multiple packages which gather data at once, when I have worked out a good code technique.

from package.weather import weatherapi
import threading

def update():
  weatherapi()
  threading.Timer(60, update).start()

update()

Firstly it just seems messy and if I wanted more packages running in a thread, I'd need to create another update function
Secondly I'm not able to kill my process

If anyone has any suggestions, it would be greatly appreciated.

Why not just use `time.sleep` for the delay? BTW if you want to exit a process without killing all threads, set their `daemon` flag to `True` before starting them. — MisterMiyagi, Jul 03 '16 at 18:04
Also have a look at this: http://stackoverflow.com/q/3393612/1025391 — moooeeeep, Jul 03 '16 at 18:27

MisterMiyagi · Accepted Answer · 2016-07-03T19:59:29.387

This is a really bad use of Threading.timer. You're constantly starting new threads, when you just want one thread to do something regularly. This code is equivalent:

from package.weather import weatherapi
import threading
import time

def update():
  while True:
    weatherapi()
    time.sleep(60)

WHEATHER_THREAD=threading.Thread(target=update)
WHEATHER_THREAD.daemon = True  # main can exit while thread is still running
WHEATHER_THREAD.start()

Since threads all use the same namespace, you can also make do with just one function.

UPDATE_CALLABLES = [weatherapi]  # add new functions to have them called by update
def update():
  while True:
    for func in UPDATE_CALLABLES:
      func()
    time.sleep(60)

Note that UPDATE_CALLABLES can also be appended while the Thread is already running.

score 0 · Answer 2 · answered Jul 03 '16 at 18:21

A class like this does what you want:

import threading

class Interval:
    def __init__(self):
        self.api=[]
        self.interval=60
        self.timer=self

    def set_api(self,api):
        self.api=api
    def set_interval(self,interval):
        self.interval=interval
    def cancel(self):
        pass
    def stop(self):
        self.timer.cancel()

    def update(self):
        for api in self.api:
            api()
        self.timer = threading.Timer(self.interval,self.update).start()

# Create instance and start with default parameters
interval=Interval()
interval.update()

# Later on change the list of items to call
interval.set_api([thisApi,thatApi])

# Later on still change the interval between calls
interval.set_interval(30)

# When you have had enough, cancel the timer
interval.stop()

Note that it still creates a new thread for each interval timed, but you can change the list of calls made at any time and stop it repeating at any time.

Python Threading timer with package

2 Answers2