I modified mawe's code so you don't have to worry about the date of the day:
# using just time and not date ...
lunch_start = datetime.time(11, 30)
lunch_end = datetime.time(12, 45)
now = datetime.datetime.now().time()
print lunch_start # 11:30:00
print lunch_end # 12:45:00
print now # eg. 09:05:59.750000
# you can compare type 'datetime.time' directly
if lunch_start < now < lunch_end:
print "Hey, it's lunch time! Mahlzeit!!"
elif now < lunch_start:
print "Lunch is pretty soon!"
print "Darn, missed lunch time!!"