Lib/test/test_xrange.py

# Python test set -- built-in functions

import test.test_support, unittest
import sys
import pickle
import itertools

import warnings
warnings.filterwarnings("ignore", "integer argument expected",
                        DeprecationWarning, "unittest")

# pure Python implementations (3 args only), for comparison
def pyrange(start, stop, step):
    if (start - stop) // step < 0:
        # replace stop with next element in the sequence of integers
        # that are congruent to start modulo step.
        stop += (start - stop) % step
        while start != stop:
            yield start
            start += step

def pyrange_reversed(start, stop, step):
    stop += (start - stop) % step
    return pyrange(stop - step, start - step, -step)


class XrangeTest(unittest.TestCase):
    def assert_iterators_equal(self, xs, ys, test_id, limit=None):
        # check that an iterator xs matches the expected results ys,
        # up to a given limit.
        if limit is not None:
            xs = itertools.islice(xs, limit)
            ys = itertools.islice(ys, limit)
        sentinel = object()
        pairs = itertools.izip_longest(xs, ys, fillvalue=sentinel)
        for i, (x, y) in enumerate(pairs):
            if x == y:
                continue
            elif x == sentinel:
                self.fail('{}: iterator ended unexpectedly '
                          'at position {}; expected {}'.format(test_id, i, y))
            elif y == sentinel:
                self.fail('{}: unexpected excess element {} at '
                          'position {}'.format(test_id, x, i))
            else:
                self.fail('{}: wrong element at position {};'
                          'expected {}, got {}'.format(test_id, i, y, x))

    def test_xrange(self):
        self.assertEqual(list(xrange(3)), [0, 1, 2])
        self.assertEqual(list(xrange(1, 5)), [1, 2, 3, 4])
        self.assertEqual(list(xrange(0)), [])
        self.assertEqual(list(xrange(-3)), [])
        self.assertEqual(list(xrange(1, 10, 3)), [1, 4, 7])
        self.assertEqual(list(xrange(5, -5, -3)), [5, 2, -1, -4])

        a = 10
        b = 100
        c = 50

        self.assertEqual(list(xrange(a, a+2)), [a, a+1])
        self.assertEqual(list(xrange(a+2, a, -1L)), [a+2, a+1])
        self.assertEqual(list(xrange(a+4, a, -2)), [a+4, a+2])

        seq = list(xrange(a, b, c))
        self.assertIn(a, seq)
        self.assertNotIn(b, seq)
        self.assertEqual(len(seq), 2)

        seq = list(xrange(b, a, -c))
        self.assertIn(b, seq)
        self.assertNotIn(a, seq)
        self.assertEqual(len(seq), 2)

        seq = list(xrange(-a, -b, -c))
        self.assertIn(-a, seq)
        self.assertNotIn(-b, seq)
        self.assertEqual(len(seq), 2)

        self.assertRaises(TypeError, xrange)
        self.assertRaises(TypeError, xrange, 1, 2, 3, 4)
        self.assertRaises(ValueError, xrange, 1, 2, 0)

        self.assertRaises(OverflowError, xrange, 10**100, 10**101, 10**101)

        self.assertRaises(TypeError, xrange, 0, "spam")
        self.assertRaises(TypeError, xrange, 0, 42, "spam")

        self.assertEqual(len(xrange(0, sys.maxint, sys.maxint-1)), 2)

        self.assertRaises(OverflowError, xrange, -sys.maxint, sys.maxint)
        self.assertRaises(OverflowError, xrange, 0, 2*sys.maxint)

        r = xrange(-sys.maxint, sys.maxint, 2)
        self.assertEqual(len(r), sys.maxint)
        self.assertRaises(OverflowError, xrange, -sys.maxint-1, sys.maxint, 2)

    def test_pickling(self):
        testcases = [(13,), (0, 11), (-22, 10), (20, 3, -1),
                     (13, 21, 3), (-2, 2, 2)]
        for proto in range(pickle.HIGHEST_PROTOCOL + 1):
            for t in testcases:
                r = xrange(*t)
                self.assertEquals(list(pickle.loads(pickle.dumps(r, proto))),
                                  list(r))

    def test_range_iterators(self):
        # see issue 7298
        limits = [base + jiggle
                  for M in (2**32, 2**64)
                  for base in (-M, -M//2, 0, M//2, M)
                  for jiggle in (-2, -1, 0, 1, 2)]
        test_ranges = [(start, end, step)
                       for start in limits
                       for end in limits
                       for step in (-2**63, -2**31, -2, -1, 1, 2)]

        for start, end, step in test_ranges:
            try:
                iter1 = xrange(start, end, step)
            except OverflowError:
                pass
            else:
                iter2 = pyrange(start, end, step)
                test_id = "xrange({}, {}, {})".format(start, end, step)
                # check first 100 entries
                self.assert_iterators_equal(iter1, iter2, test_id, limit=100)

            try:
                iter1 = reversed(xrange(start, end, step))
            except OverflowError:
                pass
            else:
                iter2 = pyrange_reversed(start, end, step)
                test_id = "reversed(xrange({}, {}, {}))".format(start, end, step)
                self.assert_iterators_equal(iter1, iter2, test_id, limit=100)


def test_main():
    test.test_support.run_unittest(XrangeTest)

if __name__ == "__main__":
    test_main()