Django snippets

def list_to_pattern(self, lst):
    ret = ''
    lst.sort()

    start = None
    # Starts from second item
    for i in range(1, len(lst)):
        # In sequence
        if lst[i] == lst[i-1] + 1:
            if start is None: start = lst[i-1]

            # Last item
            if i == len(lst) - 1:
                ret += ' %d-%d' %(start, lst[i])

        # Sequence broked
        else:
            # Last item
            if start is None:
                ret += ' %d' % lst[i-1]
            else:
                ret += ' %d-%d' %(start, lst[i])

    return ret.strip().replace(' ', ',')