Generate a random integer from several intervals

random_in_intervals.py

def random_in_intervals(allowed_intervals: Iterable):
	""" generate a radnom int from a selection of several intervals. 
	intervals have to be in the format a, b where b > a"""

	sum_of_ranges = sum(b-a for a, b in allowed_intervals)

	random_float = random.random()
	relative_number = random_float*sum_of_ranges

	# now we have to get the actual value from the interval
	passed_len = 0
	for start, end in allowed_intervals:
		length = end-start
		passed_len += length

		if passed_len >= relative_number:
			number_rest = passed_len - relative_number
			absolute_number = start + number_rest
			return round(absolute_number)
      
if __name__ == "__main__":		
	allowed_intervals = ((30, 60), (120, 150), (210, 240), (300, 330))
	rand_list = [random_in_intervals(allowed_intervals) for n in range(20)]
	print(rand_list)