return_duplicates.py

__author__ = 'szeitlin'

def return_duplicates(nums):
    """
    (list) -> (sub-list)

    look for duplicates and just return those

    >>> return_duplicates([5,5,2,3,4,5,2])
    [2, 2, 5, 5, 5]

    >>> nums = [5,2,3,4,5,2]
    >>> return_duplicates(nums)
    [2, 2, 5, 5]

    >>> nums = [5,5]
    >>> return_duplicates(nums)
    [5, 5]
    """

    seen = []

    for i in range(len(nums)):
        key = nums.pop()
        if key in nums:
            seen.append(key)
        elif key not in nums:
           if key in seen:
               seen.append(key)

        if len(nums) ==1:
            if nums in seen:
                seen.append(key)

        seen.sort()

    return seen

import doctest
doctest.testmod()