[Tutor] sorting objects in lists by 2 attr

Philippe Niquille philippe at niquille.com
Tue Jul 24 01:53:49 CEST 2007

Tanks a mill!
I don't know why I searched so far..

Anyway, I wrapped the django custom SQL call and built a nice dictionary out
of the resulting rows (which is similar to querysets). See
http://www.djangosnippets.org/snippets/207/ for details.


Am 23.07.2007 um 19:28 schrieb Eric Brunson:

Philippe Niquille wrote:


I have a hard time sorting an object list. Perhaps this is kind of a noob
question, but I would very much appreciate any help!

Using django I get a QuerySet of Score objects which are sorted by the
actual score, the actual score divided by the max. possible score (so
sorting by two db fields).

I then need to loop through that queryset and sum up all the score objects
which belong to the same user into one Score objects. This works (see code

The problem I now have, is that I lost the sorting order, as described
above. How would I resort it with a python algortithm instead of SQL?

This is not the question you're asking, but my first though was, why not
have SQL do the summing for you using sum() and group by?

scores = Score.objects.order_by('score', 'score2','owner') # filter by
course, MC !!

# loop through scores to regroup by user

newscore = []

for s in scores:

i = False

# loop through new object container and check for existant user index, add
scores if existant

for ns in newscore:

if s.owner == ns.owner:

ns.score = int(ns.score) + int(s.score)

ns.maxscore = int(ns.maxscore) + int(s.maxscore)

i = True

# otherwise append new user index object, work with it later, perhaps (if
more user objects exist)

if i == False:



I did fiddle around with .sort() but didn't get any useful results (and it
would only sort by one object..).

class CmpAttr:

def __init__(self, attr):

self.attr = attr

def __call__(self, x, y):

return cmp(getattr(x, self.attr), getattr(y, self.attr))


ps. could it be, that this maillist is blocking some e-mail addresses?


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