Missing Integers interview question

missing_ints.py

'''
Given a list of ordered integers with some of the numbers missing (and with possible    duplicates), find the missing numbers.

Example:
> missingInts([1, 3, 3, 3, 5, 6])
> 2, 4

> missingInts([1, 2, 3, 4, 4, 7, 7])
> 5, 6
'''

 def missingInts(l):
     missing = []
     prev = l[0]
     for i in range(1, len(l)):
         if l[i] == prev:
             # Duplicates, just keep moving
             continue
         elif l[i] == prev - 1:
             prev = l[i]
         else:
             missing += list(range(prev+1, l[i]))
             prev = l[i]
     return missing

 if __name__ == '__main__':
     print(missingInts([1, 3, 3, 3, 5, 6]))
     print(missingInts([1, 2, 3, 4, 4, 7, 7]))
     print(missingInts([2, 4, 7, 7]))