To execute a function after a delay or to repeat a function in given number of seconds using an event-loop (no threads), you could:
Tkinter
#!/usr/bin/env python
from Tkinter import Tk
def foo():
print("timer went off!")
def countdown(n, bps, root):
if n == 0:
root.destroy() # exit mainloop
else:
print(n)
root.after(1000 / bps, countdown, n - 1, bps, root) # repeat the call
root = Tk()
root.withdraw() # don't show the GUI window
root.after(4000, foo) # call foo() in 4 seconds
root.after(0, countdown, 10, 2, root) # show that we are alive
root.mainloop()
print("done")
Output
10
9
8
7
6
5
4
3
timer went off!
2
1
done
Gtk
#!/usr/bin/env python
from gi.repository import GObject, Gtk
def foo():
print("timer went off!")
def countdown(n): # note: a closure could have been used here instead
if n[0] == 0:
Gtk.main_quit() # exit mainloop
else:
print(n[0])
n[0] -= 1
return True # repeat the call
GObject.timeout_add(4000, foo) # call foo() in 4 seconds
GObject.timeout_add(500, countdown, [10])
Gtk.main()
print("done")
Output
10
9
8
7
6
5
4
timer went off!
3
2
1
done
Twisted
#!/usr/bin/env python
from twisted.internet import reactor
from twisted.internet.task import LoopingCall
def foo():
print("timer went off!")
def countdown(n):
if n[0] == 0:
reactor.stop() # exit mainloop
else:
print(n[0])
n[0] -= 1
reactor.callLater(4, foo) # call foo() in 4 seconds
LoopingCall(countdown, [10]).start(.5) # repeat the call in .5 seconds
reactor.run()
print("done")
Output
10
9
8
7
6
5
4
3
timer went off!
2
1
done
Asyncio
Python 3.4 introduces new provisional API for asynchronous IO — asyncio module:
#!/usr/bin/env python3.4
import asyncio
def foo():
print("timer went off!")
def countdown(n):
if n[0] == 0:
loop.stop() # end loop.run_forever()
else:
print(n[0])
n[0] -= 1
def frange(start=0, stop=None, step=1):
while stop is None or start < stop:
yield start
start += step #NOTE: loss of precision over time
def call_every(loop, seconds, func, *args, now=True):
def repeat(now=True, times=frange(loop.time() + seconds, None, seconds)):
if now:
func(*args)
loop.call_at(next(times), repeat)
repeat(now=now)
loop = asyncio.get_event_loop()
loop.call_later(4, foo) # call foo() in 4 seconds
call_every(loop, 0.5, countdown, [10]) # repeat the call every .5 seconds
loop.run_forever()
loop.close()
print("done")
Output
10
9
8
7
6
5
4
3
timer went off!
2
1
done
Note: there is a slight difference in the interface and behavior between these approaches.