Marc Tompkins wrote: > I'm working with delimited files (ANSI X12 EDI nonsense, to be > precise.) First I load the records to a list: > tmpSegs = inString.split(self.SegTerm) > > Now, I want to replace each string in that list with a string: > > for seg in tmpSegs: # 'seg' is short for 'segment' > seg = seg.split(self.ElemSep) > > It doesn't work. If I check the contents of tmpSegs, it's still a list > of strings - not a list of lists. So I do this instead: > tmpSegs2 = [] > for seg in tmpSegs: > tmpSegs2.append(seg.split(self.sElemSep)) > del tmpSegs > > This works. And, for the size of files that I'm likely to run into, > creating the extra list and burning the old one is probably not going to > swamp the machine - but it feels clumsy to me, like if I just knew the > secret I could be much more elegant about it.
Creating a new list is fine, actually. You can do it more elegantly with a list comprehension, and it's fine to assign to the same name, which will implicitly delete the old list: tmpSegs = [ seg.split(self.ElemSep) for seg in tmpSegs ] If you really want to replace elements in the same list you can use enumerate to get indices: for i, seg in enumerate(tmpSegs): tmpSegs[i] = seg.split(self.ElemSep) or use slice assignment: tmpSegs[:] = [ seg.split(self.ElemSep) for seg in tmpSegs ] but I doubt those are needed in this case. > What puzzles me most is that I can replace 'seg' with just about > anything else - > for seg in tmpSegs: > seg = seg.strip() > or > for seg in tmpSegs: > seg = 'bananas' > or > for seg in tmpSegs: > seg = seg + ' bananas' > and it works. So why can't I replace it with its own split? If by 'it works' you mean that tmpSegs is changed...you are mistaken or there is something you are not showing. Can you show why you think this changes tmpSegs? Kent _______________________________________________ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
