How do I ensure that a Python while-loop takes a particular amount of time to run?

Question

I\'m reading serial data with a while loop. However, I have no control over the sample rate.

The code itself seems to take 0.2s to run, so I know I won\'t be able to

Answer 1

Just measure the time running your code takes every iteration of the loop, and sleep accordingly:

import time

while True:
    now = time.time()            # get the time
    do_something()               # do your stuff
    elapsed = time.time() - now  # how long was it running?
    time.sleep(1.-elapsed)       # sleep accordingly so the full iteration takes 1 second

Of course not 100% perfect (maybe off one millisecond or another from time to time), but I guess it's good enough.

---

Another nice approach is using twisted's LoopingCall:

from twisted.internet import task
from twisted.internet import reactor

def do_something():
    pass # do your work here

task.LoopingCall(do_something).start(1.0)
reactor.run()