Web programming and a different "type" problem (was: Slice confusion : a[n:p] is a list exclude the last element p)

[Cameron Laird]

In article <UXara.22428$K35.745468 at news2.tin.it>,
Alex Martelli  <aleax at aleax.it> wrote:
><posted & mailed>
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>It's an important design principle because of human-factors considerations,
>which Koenig expresses better than I can (I really wish he would one day
>write a "Python Traps and Pitfalls" book, but he seems too busy writing
>great C++ books instead... perhaps the Python one would be too thin?-).  
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I'd be happy to contribute "FMM" (which I've never
bothered trademarking, though I've been tempted 
several times.

I'm looking for an idiom.  I suspect it'll interest
some of the original readers of this thread; that
vague stylistic intuition is my justification for
this hijacking.

Here's an observation:  several Python-based Web
schemes (Zope's one, I know), share what I regard as
an infelicity.  The punch-line is this:  checkboxed
data has to treat single items different from all
other multiplicities.  Pages that naturally receive
such variants as
  ...mypage?value=value0
  ...mypage?value=value1&value=value2
are interpreted as
    ...
  valuelist = Web-scheme-function('value')
  for value in valuelist:
      my_process(value)
    ...
'Doesn't work, though.  Here's where the special case
enters:  if only one datum with the indicated name is
present as input, Zope and the others return it as a
simple string, rather than a list with that string as 
its sole member.  To iterate over all checkboxed items,
therefore, in our typical Web example, one must
    ...
  valuelist = Web-scheme-function('value')
  if valuelist == str(valuelist):
      valuelist = [valuelist]
  for value in valuelist:
      my_process(value)
    ...
That's certainly ugly.

What's a better way?  Is there even a better way to 
think about this, in terms of basic Web standards?
-- 

Cameron Laird <Cameron at Lairds.com>
Business:  http://www.Phaseit.net
Personal:  http://phaseit.net/claird/home.html