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

Re: time conversions [hh:mm:ss.ms &lt;-&gt; sec(.ms)

On 28/04/2006 6:39 PM, kpp9c wrote:[color=blue]
> 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.[/color]

Could you please be a little more specific? I guess that you have
seconds-and-a-fraction in a float eg 3723.456 seconds, which is
equivalent to 1 hour, 2 minutes and 3.456 seconds. How do you want that
represented? You say hh:mm:ss.ms which could be interpreted as a string
"01:02:03.4 56" -- but this format is not very useful for "basic
arithmetic". OTOH a tuple representation like (1, 2, 3.456) can
accommodate "arithmetic " of some sort or other more easily -- is that
what you had in mind? Next question: exactly what basic arithmetic
operations do you want to do in the hour-minute-second format, and why
do you want to do them in that format, and not the seconds-only format?
[color=blue]
> I think that there just has to be a
> package
> or module out there that already does this with reasonable speed and
> accuracy.[/color]

Get the specification right first. Get the accuracy right second. Then
worry about the speed. The "arithmetic " of which you speak can't be so
mind-boggling that you can't write it in Python and test it yourself.
You may find the specification changes under the influence of the
implementation :-)
[color=blue]
>
> 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.[/color]

So why not keep it in seconds (or milliseconds)?

Have you considered an extension, using C or Pyrex?
[color=blue]
>
> i googled for hh:mm:ss.ms + python and didn't find much...
>
> best,
>
> -kp---
>
> [mac os x w/ python 2.4.1][/color]

Re: time conversions [hh:mm:ss.ms &lt;-&gt; sec(.ms)

kpp9c wrote:
[color=blue]
> 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][/color]

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.micros econd) / 1000000)

if __name__ == "__main__":
for i in (80000.123, 0.0, 5873, 12345.6789):
print "%12.6f -> %15s -> %12.6f" % (
i,
secs2time(i),
time2secs(secs2 time(i))
)
assert i == time2secs(secs2 time(i))
from timeit import Timer
timer = Timer(
setup="from __main__ import time2secs, secs2time",
stmt="time2secs (secs2time(1234 5.6789))")
count = 1000000
total = timer.timeit(co unt)
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.

--

Re: time conversions [hh:mm:ss.ms &lt;-&gt; sec(.ms)

kpp9c wrote:
[color=blue]
> 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.[/color]

Have a look at datetime.timede lta:

from datetime import timedelta

seconds_value = 4237.63
td = timedelta(secon ds=seconds_valu e)

print td # Shows 1:10:37.630000
print td.seconds # Shows 4237

other_td = td + timedelta(secon ds=13)

print other_td # Shows 1:10:50.630000
print other_td.second s # Shows 4250
[color=blue]
> I think that there just has to be a package or module out there that
> already does this with reasonable speed and accuracy.[/color]

The accuracy seems perfect, don't know about speed - take some test :)

Regards

--
Faber



We live in a society exquisitely dependent on science and technology,
in which hardly anyone knows anything about science and technology. -- Carl
Sagan

Re: time conversions [hh:mm:ss.ms &lt;-&gt; sec(.ms)

timedelta looks to be just the ticket! bravo, thank you... i guess this
must be pretty new to Python. Nice... more "batteries included"
stuff...

cheers,

-kevin--

Re: time conversions [hh:mm:ss.ms &lt;-&gt; sec(.ms)

kpp9c wrote:
[color=blue]
> timedelta looks to be just the ticket! bravo, thank you... i guess this
> must be pretty new to Python.[/color]

Well, since Python 2.3 (July 2003):


:-)

--
Faber



Only wimps use tape backup: _real_ men just upload their important stuff on
ftp and let the rest of the world mirror it  -- Linus Torvalds