Convert seconds to hh:mm:ss in Python

I can't believe any of the many answers gives what I'd consider the "one obvious way to do it" (and I'm not even Dutch...!-) -- up to just below 24 hours' worth of seconds (86399 seconds, specifically):

>>> import time
>>> time.strftime('%H:%M:%S', time.gmtime(12345))
'03:25:45'

Doing it in a Django template's more finicky, since the time filter supports a funky time-formatting syntax (inspired, I believe, from PHP), and also needs the datetime module, and a timezone implementation such as pytz, to prep the data. For example:

>>> from django import template as tt
>>> import pytz
>>> import datetime
>>> tt.Template('{{ x|time:"H:i:s" }}').render(
...     tt.Context({'x': datetime.datetime.fromtimestamp(12345, pytz.utc)}))
u'03:25:45'

Depending on your exact needs, it might be more convenient to define a custom filter for this formatting task in your app.

>>> a = datetime.timedelta(seconds=65)
datetime.timedelta(0, 65)
>>> str(a)
'0:01:05'

Code that does what was requested, with examples, and showing how cases he didn't specify are handled:

def format_seconds_to_hhmmss(seconds):
    hours = seconds // (60*60)
    seconds %= (60*60)
    minutes = seconds // 60
    seconds %= 60
    return "%02i:%02i:%02i" % (hours, minutes, seconds)

def format_seconds_to_mmss(seconds):
    minutes = seconds // 60
    seconds %= 60
    return "%02i:%02i" % (minutes, seconds)

minutes = 60
hours = 60*60
assert format_seconds_to_mmss(7*minutes + 30) == "07:30"
assert format_seconds_to_mmss(15*minutes + 30) == "15:30"
assert format_seconds_to_mmss(1000*minutes + 30) == "1000:30"

assert format_seconds_to_hhmmss(2*hours + 15*minutes + 30) == "02:15:30"
assert format_seconds_to_hhmmss(11*hours + 15*minutes + 30) == "11:15:30"
assert format_seconds_to_hhmmss(99*hours + 15*minutes + 30) == "99:15:30"
assert format_seconds_to_hhmmss(500*hours + 15*minutes + 30) == "500:15:30"

You can--and probably should--store this as a timedelta rather than an int, but that's a separate issue and timedelta doesn't actually make this particular task any easier.