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List:       python-ideas
Subject:    Re: [Python-ideas] time.Timer
From:       Andrew Barnert <abarnert () yahoo ! com>
Date:       2014-02-26 20:12:36
Message-ID: 1393445556.16309.YahooMailNeo () web181004 ! mail ! ne1 ! yahoo ! com
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From: anatoly techtonik <techtonik@gmail.com>

Sent: Tuesday, February 25, 2014 9:24 PM


> UX improvement fix for the common case:
> 
> import time
> 
> class Timer(object):
> def __init__(self, seconds):
> self.seconds = seconds
> self.restart()
> 
> def restart(self):
> self.end = time.time() + self.seconds
> 
> @property
> def expired(self):
> return (time.time() > self.end)

time.time() is almost always the wrong thing to use for almost anything. It's a \
float, it doesn't guarantee precision better than 1 second, it can be slow (on the \
order of milliseconds), and it doesn't guarantee monotonicity. You probably wanted \
monotonic here, although without knowing your use case, it's possible you wanted \
monotonic_raw with a fallback to monotonic, or perf_counter.

Also, this kind of timer is only really appropriate for a frame-loop app (as in a \
traditional arcade game or digital audio app), where you're inherently only checking, \
say, once every 20ms when idle and less often when busy. But any such loop should be \
sharing a _single_ call to the clock for the entire loop instance, not reading the \
clock repeatedly. Plus, most such programs in Python are probably written in \
something like pygame, which already provides a nicely-integrated timer (and many of \
the rest probably should be…). In an event loop, or a program based on threads or \
coroutines, or anything other than a frame loop, this is the wrong thing to do. \
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