Rob Cowie wrote: > I'm having a bit of trouble with this so any help would be gratefully > recieved... > > After splitting up a url I have a string of the form > 'tag1+tag2+tag3-tag4', or '-tag1-tag2' etc. The first tag will only be > preceeded by an operator if it is a '-', if it is preceded by nothing, > '+' is to be assumed. > > Using re.split, I can generate a list that looks thus: > ['tag1', '+', 'tag2', '+', 'tag3', '-', 'tag4'] > > I wish to derive two lists - each containing either tags to be > included, or tags to be excluded. My idea was to take an element, > examine what element precedes it and accordingly, insert it into the > relevant list. However, I have not been successful. > > Is there a better way that I have not considered? If this method is > suitable, how might I implement it? > > Thanks all, > > Rob Cowie
a = [ '+', 'tag1', '+', 'tag2', '-', 'tag3', '+', 'tag4' ] import itertools b = list(itertools.islice(a,0,8,2)) c = list(itertools.islice(a,1,8,2)) result1 = [x[1] for x in itertools.izip(b,c) if x[0] == '+'] result2 = [x[1] for x in itertools.izip(b,c) if x[0] == '-'] print print result1 print result2 Gerard -- http://mail.python.org/mailman/listinfo/python-list
