[Tutor] Functional question

[Bernard Lebel]

Thanks Kent.

I had tried the very same thing, but with a list instead of a tuple,
and got an got this:

>>> dMap[ ['allo','bonjour'] ] = 'salut'
Traceback (most recent call last):
  File "<stdin>", line 1, in ?
TypeError: list objects are unhashable

It never crossed my mind that a tuple would do it.


Thanks again.
Bernard


On 8/5/05, Kent Johnson <kent37 at tds.net> wrote:
> Bernard Lebel wrote:
> > Hello,
> >
> > This question is not strictly bound to Python, but rather some
> > functional programming problem, I hope someone can help me or suggest
> > ressources.
> >
> > 1 --
> > I have a list of lists. Each of these lists has 3 elements: a string,
> > and two integers. Thoughout the lists, there are only two different
> > integers for the first one, and two different for the second one.
> >
> > aLists = [
> >       [ 'Pass1', 10, 200 ],
> >       [ 'Pass2', 10, 200 ],
> >       [ 'Pass3', 25, 100 ],
> >       [ 'Pass4', 10, 100 ],
> >       [ 'Pass5', 25, 200 ] ]
> >
> >
> >
> > 2 --
> > Then I want to regroup the strings into two dictionaries. The first
> > dictionaries is for the strings that have the same first integer, and
> > the second dictionay is for the strings that have the same second
> > integer.
> >
> > dMap1 = {}
> > dMap2 = {}
> >
> > # Iterate lists
> > for aList in aLists:
> >
> >       sPass = aList[0]
> >       iValue1 = aList[1]
> >       iValue2 = aPList[2]
> >
> >       # Map pass name to integers
> >       dMap1.setdefault( iValue1, [] ).append( sPass )
> >       dMap2.setdefault( iValue2, [] ).append( sPass )
> 
> If I understand you correctly, you want to group the strings that have both integers the same. Just use the tuple (iValue1, iValue2) as the key in a third dictionary:
>         dmap3.setdefault( (iValue1, iValue2), [] ).append( sPass )
> 
> Kent
> 
> > So far so good, it's working, I end up with this structure:
> >
> > dMap1 = {
> >       10 : [ 'Pass1', 'Pass2', 'Pass4' ],
> >       25 : [ 'Pass3', 'Pass5' ] }
> >
> > dMap2 = {
> >       100 : [ 'Pass3', 'Pass4' ],
> >       200 : [ 'Pass1', 'Pass2', 'Pass5' ] }
> >
> >
> > 3 --
> > This is where I'm completely stump.
> > I want to consolidate the strings into another dictionary the strings
> > that share the same integers, resulting in such a structure:
> >
> > dGroups = {
> >       'group0' : [ 'Pass1', 'Pass2' ],             # 10, 200
> >       'group1' : [ 'Pass4' ],                         # 10, 100
> >       'group2' : [ 'Pass3' ],                         # 25, 100
> >       'group3' : [ 'Pass5' ],                         # 25, 200 }
> >
> > However, I have absolutely no idea how to achieve that third dictionary!
> >
> >
> >
> > Thanks
> > Bernard
> > _______________________________________________
> > Tutor maillist  -  Tutor at python.org
> > http://mail.python.org/mailman/listinfo/tutor
> >
> 
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