Generate contiguous groups of integers in python. Mostly for generating range/between + exacts in Django/Haystack where parameters may have a max count (sqlite, lucene I'm looking at you!)

be_contiguous.py

import itertools
import operator

def contiguous(unsorted):
    def grouper(value):
        return value[0] - value[1]
    data = sorted(unsorted)
    for k, g in itertools.groupby(enumerate(data), grouper):
        yield map(operator.itemgetter(1), g)

data = [4,5,6,1,10,18,22,25,26,15,16,17,27,28,29,30,31,42,52,53,54]
output = tuple(contiguous(data))
print(output)
# ([1], [4, 5, 6], [10], [15, 16, 17, 18], [22], [25, 26, 27, 28, 29, 30, 31], [42], [52, 53, 54])

def make_query(results, key):
    saved = set()
    for result in results:
        length = len(result)
        if length == 1:
            saved.add(result[0])
        elif length > 1:
            first = result[0]
            last = result[-1]
            yield {'%s__range' % key: (first, last)}
    leftover_length = len(saved)
    if leftover_length > 1:
        yield {'%s__in' % key: saved}
    elif leftover_length == 1:
        yield {'%s__exact' % key: saved[0]}

newoutput = tuple(make_query(output, 'pk'))
print(newoutput)
# ({'pk__range': (4, 6)}, {'pk__range': (15, 18)}, {'pk__range': (25, 31)}, {'pk__range': (52, 54)}, {'pk__in': set([1, 10, 42, 22])})

def or_them(results, obj_cls):
    return reduce(operator.or_, (obj_cls(**result) for result in results))

be_django_q.py

# import be_contiguous ...
from django.conf import settings
settings.configure()
from django.db.models.query_utils import Q
print(or_them(newoutput, Q))
# (OR: ('pk__range', (4, 6)), ('pk__range', (15, 18)), ('pk__range', (25, 31)), ('pk__range', (52, 54)), ('pk__in', set([1, 10, 42, 22])))