$ python
...
>>> import datetime
>>> str(datetime.timedelta(seconds=int(raw_input())))
12345
'3:25:45'
>>>

z=input('ввод числа:')
h=z/3600 
m=z%3600/60 
s=z%3600%60

print '%i:%i:%i' % (h, m, s)

datetime.datetime.now().strftime("The date is %A (%a) %d/%m/%Y"

>>> import time
>>> s = time.localtime(12345)
>>> print(s.tm_hour, s.tm_min, s.tm_sec, sep=':') # python 3.x
14:25:45
>>> s
time.struct_time(tm_year=1970, tm_mon=1, tm_mday=1, tm_hour=14, tm_min=25, tm_sec=45, tm_wday=3, tm_yday=1, tm_isdst=0)
>>>