Define a range, return all numbers of range that are NOT in csv data

[ichabod801]

Analysis looks correct. A nested dict (just like the one you used in post #11) should work. Note that my code assumed a list of number ranges, and I also messed up the call to in_range. It should be more like this for nested dicts:

def find_range(n):
    for num_range in _number_ranges.values():
        if in_range(n, num_range):
            break
    return num_range