Op Thursday 30 Apr 2015 11:30 CEST schreef Peter Otten: > Cecil Westerhof wrote: > >> I have a function to fetch a message from a file: >> def get_indexed_message(message_filename, index): >> """ >> Get index message from a file, where 0 gets the first message >> """ >> >> return open(expanduser(message_filename), >> 'r').readlines()[index].rstrip() >> >> What is more the Python way: let the exception fire like this code >> when index is to big, or catching it and returning None? > > Fire an exception, but you may also allow the user to provide a > default. > >> I suppose working zero based is OK. > > Not just OK, it's de rigueur. > > > You didn't ask for that, but > > (1) > > with open(...) as f: > return f.readlines()[index].rstrip() > > is preferrable because it closes the file in a controlled way and
I already did that. In another thread I got to know my assumptions where wrong. > (2) you may want to take measures to limit memory usage, e. g. > > assert index >= 0 I put that in, but as first statement. > try: > [line] = itertools.islice(f, index, index+1) > except ValueError: > raise IndexError > return line.rstrip() In my case it is not important. (The biggest file I use has between 100 and 200 lines), but I publish it, so I should do my best to make it so lean as possible. To quote a famous comedian: ‘Learning all the time’. -- Cecil Westerhof Senior Software Engineer LinkedIn: http://www.linkedin.com/in/cecilwesterhof -- https://mail.python.org/mailman/listinfo/python-list
