How to convert time format into milliseconds and back in Python?

The reason is because I'm making a script to work with ffmpeg and I need to be able to add/subtract time in the format 00:00:00[.000]

The last 3 digits are optional and they mean milliseconds. A time string could look like any of the following

4:34.234
5.000
2:99:34
4:14

This would be easier if a lot of the digits weren't optional. But since they are, I'm thinking I have to use some sort of regex to parse i开发者_StackOverflow社区t?

From string to milliseconds:

s = "4:34.234"
hours, minutes, seconds = (["0", "0"] + s.split(":"))[-3:]
hours = int(hours)
minutes = int(minutes)
seconds = float(seconds)
miliseconds = int(3600000 * hours + 60000 * minutes + 1000 * seconds)

From milliseonds to string:

hours, milliseconds = divmod(miliseconds, 3600000)
minutes, milliseconds = divmod(miliseconds, 60000)
seconds = float(milliseconds) / 1000
s = "%i:%02i:%06.3f" % (hours, minutes, seconds)

from time import time

time_in_seconds = int(time())
time_in_miliseconds = int(time_in_seconds *1000)

You can also use str(x) to convert x to a string. From there you can use various methods to create the string you want, such as: (both of these assume you already have the variables hrs, min, sec, msec with the values you want)

str(hrs) + ':' + str(min) + ':' + str(sec) + '.' + str(msec)

or, more pythonically:

'{hrs}:{min}:{sec}.{msec}'.format(hrs = str(hrs), min = str(min), sec = str(sec), msec = str(msec))

Furthermore, you could use the strftime() function in the time module if you wanted to use the current time. check out http://docs.python.org/library/time.html