[Gramps-devel] New Python 2.3 class: sets

[Lorenzo C. <l_c...@ev...>]

Hi everybody,

I noticed that there's a new class available in the Python library 
starting from version 2.3.  Its name is "sets" 
(</usr/share/doc/python2.3/html/lib/module-sets.html> if you're using 
Debian).

I wanted to point it out, because I think it's of special interest for 
GRAMPS.  Class "sets", as its name says, has been written to deal with 
sets of objects.  A set is similar to a list, but it differs for a 
substatial property: objects are unique within a given set.

As you may guess, GRAMPS' task is foundamentally to work with sets. 
There cannot be two individuals, families, places, sources, etc, with 
the same ID.  Hence, a collection of individuals is more properly a set, 
not a list (not in all cases, of course).

The main advantage of using the sets class over a bare list object is
that membership tests are carried out as O(1) rather than O(n/2) as for
lists.  Sets class also comes with a heap of useful functions like
union, intersection, difference, etc.

I played a little with the relationship graph (plugins/Graphvix.py) and 
I was able to boost up graph generation by a factor of 10 or so.

I think that the porting from a pure list-based source code to a mixed
list-set one is quite simple.  Sets can be iterated over as it happens
with lists; membership and non-membership tests are in the form of "x in
s" and "x not in s" rispectively, like lists.  Only the list.append()
function has been replaced by set.add().

I hope you'll find sets class useful.

-- 
email: lor...@em...
Jabber: lo...@li...
Fingerprint: 8CDD 3408 53B2 6122 99DA EE37 1523 68FC D906 4C08

Vuoi aiutarci ad avere le descrizioni dei pacchetti Debian in italiano?
http://ddtp.debian.org/