Trace of lazy set implementation in Python

lazy_set.py

# Copyright (C) 2011 by Enrico Franchi
#
# This file is released under the terms of the MIT license
# http://www.opensource.org/licenses/mit-license.php

import itertools as it

def silence_generator_already_executing(generator):
    try:
        for element in generator:
            yield element
    except ValueError, e:
        pass

class lazy_set(object):
    """
    Trace of implementation of lazy sets in Python.
    """
    def __init__(self, input_=[]):
        self.input_ = iter(input_)
        self.seen = set()

    def _iter(self):
        for element in self.input_:
            if element in self.seen:
                continue
            else:
                yield element
                self.seen.add(element)

    def add(self, obj):
        self.seen.add(obj)

    def update(self, iterator):
        self.input_ = it.chain(self.input_,
            silence_generator_already_executing(iterator))

    def __iter__(self):
        return it.chain(self.seen, self._iter())


if __name__ == "__main__":
    import doctest
    doctest.testmod()

lazy_set_test.py

import unittest
import lazy_set

class LazySetTest(unittest.TestCase):
    def setUp(self):
        self.lazy_set = lazy_set.lazy_set(xrange(1, 4))
        self.starting_value = range(1, 4)

    def testCreation(self):
        self.assertEqual(
            sorted(self.lazy_set),
            self.starting_value
        )

    def testUpdate(self):
        self.lazy_set.update(2* x for x in range(4, 10))
        self.assertEqual(
            sorted(self.lazy_set),
            [1, 2, 3, 8, 10, 12, 14, 16, 18]
        )

    def testAdd(self):
        self.lazy_set.add(5)
        self.assertEqual(
            sorted(self.lazy_set),
            [1, 2, 3, 5]
        )

    def testUniqueness(self):
        self.lazy_set.update(xrange(5))
        self.lazy_set.update(xrange(3, 8))
        self.assertEqual(
            sorted(self.lazy_set),
            range(8)
        )

    def testSelfUpdateWIter(self):
        self.lazy_set.update(iter(self.lazy_set))
        self.assertEqual(
            sorted(self.lazy_set),
            self.starting_value
        )

    def testSelfUpdateWOIter(self):
        self.lazy_set.update(self.lazy_set)
        self.assertEqual(
            sorted(self.lazy_set),
            self.starting_value
        )

    def testSelfUpdateNotLats(self):
        self.lazy_set.update(iter(self.lazy_set))
        self.lazy_set.update(xrange(5, 8))
        self.assertEqual(
            sorted(self.lazy_set),
            range(1, 4) + range(5, 8)
        )

if __name__ == '__main__':
    unittest.main()

Please, do not consider my last post as "this kind of stuff is not relevant". It is good to consider readability, style and efficiency (in this order) when writing code. It is the only way to improve. In pair programming, it would be the navigator to consider these issues.