Fill up a container, to some numerical limit, from another container dependent on some predicate between the item and the dependent container.

fill

""" Fill up a container, to some numerical limit, from another container
    dependent on some predicate between the item and the dependent
    container. """

from itertools import takewhile
import unittest


def fill(source, destination, limit, predicate):

    iterator = source.__iter__()

    while len(destination) != limit:
        item = iterator.next()

        if predicate(destination, item):
            destination.append(item)

class TestUniqueFill(unittest.TestCase):

    def setUp(self):

        self.source = ['a', 'c', 'a', 'b', 'a', 'c', 'd']
        self.destination = []

    def test_fill(self):

        fill(self.source, self.destination, 3, lambda d, i: i not in d)

        self.assertEquals(
            self.destination,
            ['a', 'c', 'b']
        )

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