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('{0}: iterator ended unexpectedly '
                          'at position {1}; expected {2}'.format(test_id, i, y))
            elif y == sentinel:
                self.fail('{0}: unexpected excess element {1} at '
                          'position {2}'.format(test_id, x, i))
            else:
                self.fail('{0}: wrong element at position {1};'
                          'expected {2}, got {3}'.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.assert_(a in seq)
        self.assert_(b not in seq)
        self.assertEqual(len(seq), 2)

        seq = list(xrange(b, a, -c))
        self.assert_(b in seq)
        self.assert_(a not in seq)
        self.assertEqual(len(seq), 2)

        seq = list(xrange(-a, -b, -c))
        self.assert_(-a in seq)
        self.assert_(-b not in 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, 1e100, 1e101, 1e101)

        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({0}, {1}, {2})".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({0}, {1}, {2}))".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()