[Tutor] In-place expansion of list members... possible?

[Marc Tompkins]

This question has probably been asked and answered many times, but I can't
figure out how to word my question to get relevant results from Google.  So
I thought I'd try some human beings, eh?

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.  I don't want the next guy who
reads my code to scratch his head and say 'What was he thinking?' -
especially if it's me in a year's time!

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?

It's not a burning question - development continues - but I'm really
curious.

Thanks!
-- 
www.fsrtechnologies.com
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