time conversions [hh:mm:ss.ms <-> sec(.ms)

[Dave Hughes]

kpp9c wrote:

> Hi,
> 
> I was looking at python & datetime and hoping that it would already
> have
> a method/func to translate time formats. I need to translate seconds
> to hh:mm:ss.ms and vice versa and would like the ability to do some
> basic arithmetic in these formats. I think that there just has to be a
> package
> or module out there that already does this with reasonable speed and
> accuracy.
> 
> Sadly, i do indeed need both reasonable speed and accuracy since i
> will be adding up huge masses of small events (around 10 to 60 ms
> milliseconds
> in length) to create cloud like textures for real time audio/video at
> high sampling rates.
> 
> i googled for hh:mm:ss.ms + python and didn't find much...
> 
> best,
> 
> -kp---
> 
> [mac os x w/ python 2.4.1]

Hmmm ... not difficult to do, but it's the "speed" bit that's tricky.
Here's quick and dirty implementation, but I wouldn't place any bets on
it being fast (or accurate enough for that matter!)

#!/bin/env python
# vim: set noet sw=4 ts=4:

import datetime

def secs2time(s):
    ms = int((s - int(s)) * 1000000)
    s = int(s)
    # Get rid of this line if s will never exceed 86400
    while s >= 24*60*60: s -= 24*60*60
    h = s / (60*60)
    s -= h*60*60
    m = s / 60
    s -= m*60
    return datetime.time(h, m, s, ms)

def time2secs(d):
    return d.hour*60*60 + d.minute*60 + d.second + \
        (float(d.microsecond) / 1000000)

if __name__ == "__main__":
    for i in (80000.123, 0.0, 5873, 12345.6789):
        print "%12.6f -> %15s -> %12.6f" % (
            i,
            secs2time(i),
            time2secs(secs2time(i))
        )
        assert i == time2secs(secs2time(i))
    from timeit import Timer
    timer = Timer(
        setup="from __main__ import time2secs, secs2time",  
        stmt="time2secs(secs2time(12345.6789))")
    count = 1000000
    total = timer.timeit(count)
    print "Time for %d invocations: %.10fs" % (count, total)
    print "Time per invocation: %.10fs" % (total / count,)


And the output:

80000.123000 -> 22:13:20.123000 -> 80000.123000
    0.000000 ->        00:00:00 ->     0.000000
 5873.000000 ->        01:37:53 ->  5873.000000
12345.678900 -> 03:25:45.678900 -> 12345.678900
Time for 1000000 invocations: 9.3959178925s
Time per invocation: 0.0000093959s


Huh ... what d'ya know ... good thing I ain't a betting man!


Dave.

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