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sort_by_id_sequence

Author:
simon
Posted:
May 15, 2008
Language:
Python
Version:
.96
Tags:
sorting
Score:
0 (after 0 ratings)

I needed to sort a set of objects (a QuerySet for example) by an externally provided list of IDs - for example:

>>> writers = Writer.objects.all()
>>> sort_by_id_sequence(writers, [3, 1, 2])
[<Writer id: 3>, <Writer id: 1>, <Writer id: 2>]
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def sort_by_id_sequence(objects, id_sequence):
    max_score = len(objects)
    def sort_score_for_object(obj):
        # A lower score is better
        id = obj.id
        try:
            return id_sequence.index(id)
        except ValueError: # Not found
            return max_score
    return sorted(objects, key=sort_score_for_object)

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