def uniques_only(iterable):
    """
    Function that accepts an iterable and returns a new iterable 
    with all items from the original iterable except for duplicates.
    """
    uniques_dict = {}
    
    for item in iterable:
        if item not in uniques_dict:
            uniques_dict[item] = 1
            yield item

list(uniques_only([1, 2, 2, 1, 1, 3, 2, 1]))

nums = [1, -3, 2, 3, -1]
squares = (n**2 for n in nums)

list(uniques_only(squares))

uniques_only([1, 2, 2, 1, 1, 3, 2, 1])

list(uniques_only({'a': 1, 'b':2, 'c': 3}))

"""
Explanation: Bonus1: return an iterator (for example a generator) from your uniques_only function instead of a list
End of explanation
"""


list(uniques_only([['a', 'b'], ['a', 'c'], ['a', 'b']]))


def uniques_only(iterable):
    """
    Function that accepts an iterable and returns a new iterable 
    with all items from the original iterable except for duplicates.
    """
    uniques_dict = {}
    
    for item in iterable:
        item = tuple(item) 
        if item not in uniques_dict:
            uniques_dict[item] = 1
            yield item

list(uniques_only([['a', 'b'], ['a', 'c'], ['a', 'b']]))

list(uniques_only([1, 2, 2, 1, 1, 3, 2, 1]))

def uniques_only(iterable):
    """
    Function that accepts an iterable and returns a new iterable 
    with all items from the original iterable except for duplicates.
    """
    uniques_dict = {}
    
    for item in iterable:
        try:
            hashed = tuple(item)
        except TypeError:
            hashed = item
            
        if hashed not in uniques_dict:
            uniques_dict[hashed] = 1
            yield item

list(uniques_only([1, 2, 2, 1, 1, 3, 2, 1]))

nums = [1, -3, 2, 3, -1]
squares = (n**2 for n in nums)

list(uniques_only(squares))

list(uniques_only([['a', 'b'], ['a', 'c'], ['a', 'b']]))

from timeit import default_timer
import unittest

class UniquesOnlyTests(unittest.TestCase):

    """Tests for uniques_only."""

    def assertIterableEqual(self, iterable1, iterable2):
        self.assertEqual(list(iterable1), list(iterable2))

    def test_no_duplicates(self):
        self.assertIterableEqual(uniques_only([1, 2, 3]), [1, 2, 3])

    def test_adjacent_duplicates(self):
        self.assertIterableEqual(uniques_only([1, 1, 2, 2, 3]), [1, 2, 3])

    def test_non_adjacent_duplicates(self):
        self.assertIterableEqual(uniques_only([1, 2, 3, 1, 2]), [1, 2, 3])

    def test_lots_of_duplicates(self):
        self.assertIterableEqual(uniques_only([1, 2, 2, 1, 1, 2, 1]), [1, 2])

    def test_accepts_iterator(self):
        nums = (n**2 for n in [1, 2, 3])
        self.assertIterableEqual(uniques_only(nums), [1, 4, 9])

    # To test the Bonus part of this exercise, comment out the following line
    # @unittest.expectedFailure
    def test_returns_iterator(self):
        nums = iter([1, 2, 3])
        output = uniques_only(nums)
        self.assertEqual(iter(output), iter(output))
        self.assertEqual(next(output), 1)
        self.assertEqual(next(nums), 2)

    # To test the Bonus part of this exercise, comment out the following line
    # @unittest.expectedFailure
    def test_accepts_nonhashable_types(self):
        output = uniques_only([[1, 2], [3], [1], [3]])
        self.assertIterableEqual(output, [[1, 2], [3], [1]])

    # To test the Bonus part of this exercise, comment out the following line
    # @unittest.expectedFailure
    def test_hashable_types_faster(self):
        hashables = [(n,) for n in range(4000)] + [0]
        unhashables = [[n] for n in range(4000)] + [0]
        with Timer() as hashable:
            for _ in uniques_only(hashables):
                pass
        with Timer() as unhashable:
            for _ in uniques_only(unhashables):
                pass
        self.assertLess(hashable.elapsed * 5, unhashable.elapsed)


class Timer:

    """Context manager to time a code block."""

    def __enter__(self):
        self.start = default_timer()
        return self

    def __exit__(self, *args):
        self.end = default_timer()
        self.elapsed = self.end - self.start


if __name__ == "__main__":
    unittest.main(argv=['first-arg-is-ignored'], exit=False)

"""
Explanation: Bonus2: allow your uniques_only function to work with unhashable objects
End of explanation
"""


