I would definitely use such a construction. It would be nice to have a
data structure that behaves like 1:1 correspondence or as in your case 1 to
many correspondances instead of needing to keep two dictionaries. It would
make life a lot easier because you loose the need of a double
administration. I.e. if you now want to remove 'c' from d in your example
you would need to do:
v = d.pop('c')
d_inv[v].remove('c')
it would by much nicer (and less error prone) if one could just do:
del d['c']
Le mercredi 25 septembre 2013 18:08:12 UTC+2, Nathann Cohen a écrit :
>
> Helloooooooo everybody !
>
> I was just messing with dictionaries and lists, and I wonder if we
> could solve the problem once and for all with an inefficient generic
> solution. Here's the thing :
>
> I often have to define both a function, and its inverse. Something like :
>
> d = {
> 'a' : 1,
> 'b' : 2,
> 'c' : 1,
> 'd' : 3
> }
>
> Then, I want to find the list of all elements whose image is a 1, or
> 2, or 3, and end up defining the following dictionary :
>
> d_inv = {
> 1 : ['a','c'],
> 2 : ['b'],
> 3 : ['d']
> }
>
> Aaaaaand it would be sooo nice if there was a way to write d**(-1)[2],
> or something of the kind ! Did you ever write a code like this, and
> would you be interested by a generic tool for that ?
>
> Otherwise I'll just keep on computing the inverse of my dictionaries
> with a couple of Python lines ;-)
>
> Have fuuuuuuuun !
>
> Nathann
>
--
You received this message because you are subscribed to the Google Groups
"sage-devel" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to sage-devel+unsubscr...@googlegroups.com.
To post to this group, send email to sage-devel@googlegroups.com.
Visit this group at http://groups.google.com/group/sage-devel.
For more options, visit https://groups.google.com/groups/opt_out.
