Challenge

availability_2.py

def availability(start, end, blocks):
    """Return a new list of tuples of ints, where those ints
    represent the time ranges between start and end that
    don't intersect with any blocks.

    Keyword arguments:
    start -- earliest start time we care about
    end -- latest end time we care about
    blocks -- list of tuples of ints that we wish to exclude
    return -- list of tuples of ints
    """
    pair = []
    pairs = []
    current = start
    unavailability = set([i for block in blocks for i in range(block[0] + 1, block[1])])
    while current >= start and current <= end:
        valid = current not in unavailability
        if valid:
            pair.append(current)
        elif not valid and pair:
            pairs.append((min(pair), max(pair)))
            pair = []

        current += 1
    
    pairs.append((min(pair), max(pair)))

    return pairs


print availability(1, 5, [(2,4)]) # [(1, 2), (4, 5)]
print availability(1, 5, []) # [(1, 5)]
print availability(2, 5, [(1,3)]) # [(3, 5)]
print availability(1, 10, [(2,6), (5,9)]) # [(1, 2), (9, 10)] << Overlapping unavailability block