time_average.py

from datetime import datetime

def time_average(time_1, time_2):
	"""
	return a the average time between time_1 and time_2
	as a string in the same format as the input
	"""

	FMT = '%M:%S:%f'

	try:
		time_1 = datetime.strptime(time_1, FMT)
		time_2 = datetime.strptime(time_2, FMT)

		mid = time_1 + (time_2 - time_1) / 2

		return mid.strftime(FMT)[:-4]

	except TypeError, e:
		print 'Wrong input parameter %s' % e
	except ValueError, e:
		print 'Time format not valid %s' % e



import unittest

class TestTimeAverage(unittest.TestCase):

	def setUp(self):
	 	pass

	def test_none_time(self):

		self.assertEqual(time_average(None, None), None)

	def test_wrong_format(self):

		self.assertEqual(time_average('test', 'test'), None)

	def test_ok(self):

		self.assertEqual(time_average( '30:00:00', '10:00:00'), '20:00:00')

	def test_t1gt2(self):
		"""
		t1 is greater than t2
		"""

		self.assertEqual(time_average( '10:00:00', '20:00:00'), '15:00:00')

	def test_ok_ms(self):
		"""
		t1 is greater than t2
		"""

		self.assertEqual(time_average( '00:55:00', '01:00:00'), '00:57:50')

	def tearDown(self):
	 	pass