Paul Hankin <[EMAIL PROTECTED]> wrote: > On Apr 3, 12:37 pm, [EMAIL PROTECTED] wrote: > > What's the neatest and/or most efficient way of testing if one of a > > set of strings (contained in a dictionary, list or similar) is a > > sub-string of a given string? > > > > I.e. I have a string delivered into my program and I want to see if > > any of a set of strings is a substring of the string I have been > > given. It's quite OK to stop at the first one found. Ideally the > > strings being searched through will be the keys of a dictionary but > > this isn't a necessity, they can just be in a list if it could be done > > more efficiently using a list. > > > > Is this the best one can do (ignoring the likelihood that I've got > > some syntax wrong) :- > > > > # l is the list > > # str is the incoming string > > answer = "" > > for x in l: > > if str.find(x) < 0: > > continue > > answer = x > > I'd not use 'l' (confused with '1') or 'str' (a standard module) as > variable names.
Neither would I, it was just thrown together to show how I was thinking. > Your code checks every string in the list even when > it's found one... you can reverse the test and break when the first > one is found. Using 'in' rather than testing the return value of find > is nicer as a substring test. Finally, using the 'else' clause lets > you make it clear that answer is set to the empty string when no match > is found. > > for answer in l: > if str in answer: break > else: > answer = '' > OK, that does improve things somewhat, thanks. -- Chris Green -- http://mail.python.org/mailman/listinfo/python-list
