Don't use strptime, use a regex

I am using Python to do some data file processing, converting data from a horrendously verbose, repetitive format to a nice, clean, CSV format. The date and time are in two different fields, and the date is in MM/DD/YYYY format, plus, the MM and DD might be one or two characters. That is, January is 1, not 01.

I am converting the timestamp to ISO format, so I was using time.strptime to extract the date/time and time.strftime to generate to proper ISO formatted date, like so:


On the smallest of my data files, the processing was taking 13 to 15 seconds. I profiled it, and found that in a 13 second run, strptime was taking 8.755 seconds of that, and it was calling _getlang(), _parse_localename(), and the like very time.

So, thought I, regexes are pretty efficient, I wonder if that would reduce the run time any.


(The re.compile() call is at the module level, outside the function, so it is only run once.)

My overall run time dropped to about 5 seconds, a little over 1/3 of the time it took previously. My convert_timestamp() function, which previously had consumed nearly 10 seconds, was only taking about 1.3 seconds now.

Sometimes regexes are the answer.