how do i filter an itertools chain() result?

Question

in my views, if i import an itertools module:

from itertools import chain

and i chain some objects with it:

franktags = Frank.objects.order_by('date_added').reverse().filter(topic__exact='art') 
amytags = Amy.objects.order_by('date_added').reverse().filter(topic__exact='art') 
timtags = Tim.objects.order_by('date_added').reverse().filter(topic__exact='art') 
erictags = Eric.objects.order_by('date_added').reverse().filter(topic__exact='art')

ourtags = list(chain(franktags, amytags, timtags, erictags))

how do i then order "ourtags" by the "date_added"?

not surpisingly,

ourtags = list(chain(franktags, amytags, timtags, erictags)).order_by('date_added')

returns an "'list' object has no attribute 'order_by'" error.

Answer 1

import operator

ourtags = sorted(ourtags, key=operator.attrgetter('date_added'))

Answer 2

By this point in the code, you've already loaded up all of the objects into memory and into a list. Just sort the list like you would any old Python list.

>>> import operator
>>> ourtags.sort(key=operator.attrgetter('date_added'))