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Date: Wed, 29 Jun 2011 08:56:35 +1000
Subject: Re: Suppressing newline writing to file after variable
From: Chris Angelico <rosuav@gmail.com>
To: python-list@python.org
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On Wed, Jun 29, 2011 at 3:32 AM, Ellerbee, Edward <EEllerbee@bbandt.com> wrote:
> How to condense a group of numbers to a wildcard list. For example:
>
> 252205
> 252206
> 252208
>
> Condense to:
> 25220[568]

Assuming you have the list sorted (if not, that's the first place to
start), I'd do a six-pass approach - one pass for each digit. It's
simple and readable, and I doubt you'll be working with enough numbers
for its inefficiency to be a problem. Something like this (untested
code):

lastprefix=tails=None
for cur in list_of_numbers:
  prefix=cur[:5]; tail=cur[5]
  if prefix!=lastprefix:
    if lastprefix!=None:
      if len(tails)>1: emit("%s[%s]"%(lastprefix,tails))
      else emit(lastprefix+tails)
    lastprefix,tails=prefix,""
  tails+=tail
if lastprefix!=None:
  if len(tails)>1: emit("%s[%s]"%(lastprefix,tails))
  else emit(lastprefix+tails)

Feed the emitted results from this pass into the next pass, in which
prefix is cur[:4] and tail is cur[4], etc. For the subsequent passes,
you'll also need to worry about a suffix (which would be cur[5:] when
you're looking at cur[4]), and ensure that that matches, same as the
prefix.

This is completely untested, but it should be a start. (Replace the
calls to the imaginary "emit" function with whatever you do to emit
results - for the intermediate passes, that's probably appending to a
list.)

Chris Angelico