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Avoid signed overflow in some xrange calculations, and extend

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xrange tests to cover some special cases that caused problems
in py3k.  This is a partial backport of r76292-76293 (see
issue #7298.)
This commit is contained in:
Mark Dickinson 2009-11-15 12:31:13 +00:00
parent 20eb4f0782
commit 009ae861f2
2 changed files with 112 additions and 34 deletions
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68
Lib/test/test_xrange.py
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@ -3,12 +3,49 @@
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])
@ -67,6 +104,37 @@ class XrangeTest(unittest.TestCase):
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)