def missing(numranges):
    (minimum, maximum) = (min(map(lambda x: x[0], numranges)),
                          max(map(lambda x: x[1], numranges)))
    (count, i) = (0, minimum)

    while i < maximum:
        if any(j <= i <= k for j, k in numranges):
            count += 1
        i += 1

return maximum - minimum - count

def missing(numranges):
    number_of_missing = 0
    for i, range in enumerate(numranges):
        if i == len(numranges)-1:
            break
        if numranges[i+1][0] != numranges[i][1]+1:
            number_of_missing += numranges[i+1][0] - numranges[i][1] - 1
    return number_of_missing

test = set(range(1, 100 + 1) + range(102, 200 + 1))
missing = list(set(range(min(test), max(test))) - test)
print (missing)

In [22]: input_list = [range(1,100),range(102, 200)]
In [23]: total_list = sum(input_list,[])
In [24]: master_total_list = range(min(total_list),max(total_list)+1)
In [25]: [i for i in master_total_list if i not in total_list]
Out[25]: [100, 101]

>>> l = [[1, 50] ,[55, 90], [95, 100]]
>>> sum([l[i+1][0]-m[1]-1 for i, m in enumerate(l[:-1])])
8