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256 lines
8.2 KiB
256 lines
8.2 KiB
2 years ago
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# tests for slice objects; in particular the indices method.
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import itertools
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import operator
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import sys
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import unittest
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import weakref
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from pickle import loads, dumps
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from test import support
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def evaluate_slice_index(arg):
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"""
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Helper function to convert a slice argument to an integer, and raise
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TypeError with a suitable message on failure.
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"""
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if hasattr(arg, '__index__'):
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return operator.index(arg)
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else:
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raise TypeError(
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"slice indices must be integers or "
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"None or have an __index__ method")
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def slice_indices(slice, length):
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"""
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Reference implementation for the slice.indices method.
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"""
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# Compute step and length as integers.
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length = operator.index(length)
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step = 1 if slice.step is None else evaluate_slice_index(slice.step)
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# Raise ValueError for negative length or zero step.
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if length < 0:
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raise ValueError("length should not be negative")
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if step == 0:
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raise ValueError("slice step cannot be zero")
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# Find lower and upper bounds for start and stop.
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lower = -1 if step < 0 else 0
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upper = length - 1 if step < 0 else length
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# Compute start.
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if slice.start is None:
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start = upper if step < 0 else lower
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else:
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start = evaluate_slice_index(slice.start)
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start = max(start + length, lower) if start < 0 else min(start, upper)
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# Compute stop.
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if slice.stop is None:
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stop = lower if step < 0 else upper
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else:
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stop = evaluate_slice_index(slice.stop)
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stop = max(stop + length, lower) if stop < 0 else min(stop, upper)
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return start, stop, step
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# Class providing an __index__ method. Used for testing slice.indices.
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class MyIndexable(object):
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def __init__(self, value):
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self.value = value
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def __index__(self):
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return self.value
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class SliceTest(unittest.TestCase):
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def test_constructor(self):
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self.assertRaises(TypeError, slice)
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self.assertRaises(TypeError, slice, 1, 2, 3, 4)
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def test_repr(self):
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self.assertEqual(repr(slice(1, 2, 3)), "slice(1, 2, 3)")
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def test_hash(self):
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# Verify clearing of SF bug #800796
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self.assertRaises(TypeError, hash, slice(5))
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with self.assertRaises(TypeError):
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slice(5).__hash__()
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def test_cmp(self):
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s1 = slice(1, 2, 3)
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s2 = slice(1, 2, 3)
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s3 = slice(1, 2, 4)
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self.assertEqual(s1, s2)
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self.assertNotEqual(s1, s3)
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self.assertNotEqual(s1, None)
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self.assertNotEqual(s1, (1, 2, 3))
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self.assertNotEqual(s1, "")
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class Exc(Exception):
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pass
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class BadCmp(object):
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def __eq__(self, other):
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raise Exc
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s1 = slice(BadCmp())
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s2 = slice(BadCmp())
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self.assertEqual(s1, s1)
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self.assertRaises(Exc, lambda: s1 == s2)
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s1 = slice(1, BadCmp())
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s2 = slice(1, BadCmp())
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self.assertEqual(s1, s1)
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self.assertRaises(Exc, lambda: s1 == s2)
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s1 = slice(1, 2, BadCmp())
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s2 = slice(1, 2, BadCmp())
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self.assertEqual(s1, s1)
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self.assertRaises(Exc, lambda: s1 == s2)
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def test_members(self):
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s = slice(1)
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self.assertEqual(s.start, None)
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self.assertEqual(s.stop, 1)
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self.assertEqual(s.step, None)
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s = slice(1, 2)
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self.assertEqual(s.start, 1)
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self.assertEqual(s.stop, 2)
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self.assertEqual(s.step, None)
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s = slice(1, 2, 3)
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self.assertEqual(s.start, 1)
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self.assertEqual(s.stop, 2)
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self.assertEqual(s.step, 3)
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class AnyClass:
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pass
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obj = AnyClass()
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s = slice(obj)
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self.assertTrue(s.stop is obj)
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def check_indices(self, slice, length):
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try:
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actual = slice.indices(length)
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except ValueError:
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actual = "valueerror"
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try:
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expected = slice_indices(slice, length)
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except ValueError:
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expected = "valueerror"
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self.assertEqual(actual, expected)
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if length >= 0 and slice.step != 0:
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actual = range(*slice.indices(length))
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expected = range(length)[slice]
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self.assertEqual(actual, expected)
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def test_indices(self):
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self.assertEqual(slice(None ).indices(10), (0, 10, 1))
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self.assertEqual(slice(None, None, 2).indices(10), (0, 10, 2))
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self.assertEqual(slice(1, None, 2).indices(10), (1, 10, 2))
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self.assertEqual(slice(None, None, -1).indices(10), (9, -1, -1))
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self.assertEqual(slice(None, None, -2).indices(10), (9, -1, -2))
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self.assertEqual(slice(3, None, -2).indices(10), (3, -1, -2))
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# issue 3004 tests
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self.assertEqual(slice(None, -9).indices(10), (0, 1, 1))
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self.assertEqual(slice(None, -10).indices(10), (0, 0, 1))
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self.assertEqual(slice(None, -11).indices(10), (0, 0, 1))
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self.assertEqual(slice(None, -10, -1).indices(10), (9, 0, -1))
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self.assertEqual(slice(None, -11, -1).indices(10), (9, -1, -1))
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self.assertEqual(slice(None, -12, -1).indices(10), (9, -1, -1))
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self.assertEqual(slice(None, 9).indices(10), (0, 9, 1))
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self.assertEqual(slice(None, 10).indices(10), (0, 10, 1))
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self.assertEqual(slice(None, 11).indices(10), (0, 10, 1))
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self.assertEqual(slice(None, 8, -1).indices(10), (9, 8, -1))
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self.assertEqual(slice(None, 9, -1).indices(10), (9, 9, -1))
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self.assertEqual(slice(None, 10, -1).indices(10), (9, 9, -1))
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self.assertEqual(
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slice(-100, 100 ).indices(10),
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slice(None).indices(10)
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)
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self.assertEqual(
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slice(100, -100, -1).indices(10),
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slice(None, None, -1).indices(10)
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)
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self.assertEqual(slice(-100, 100, 2).indices(10), (0, 10, 2))
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self.assertEqual(list(range(10))[::sys.maxsize - 1], [0])
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# Check a variety of start, stop, step and length values, including
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# values exceeding sys.maxsize (see issue #14794).
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vals = [None, -2**100, -2**30, -53, -7, -1, 0, 1, 7, 53, 2**30, 2**100]
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lengths = [0, 1, 7, 53, 2**30, 2**100]
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for slice_args in itertools.product(vals, repeat=3):
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s = slice(*slice_args)
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for length in lengths:
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self.check_indices(s, length)
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self.check_indices(slice(0, 10, 1), -3)
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# Negative length should raise ValueError
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with self.assertRaises(ValueError):
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slice(None).indices(-1)
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# Zero step should raise ValueError
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with self.assertRaises(ValueError):
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slice(0, 10, 0).indices(5)
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# Using a start, stop or step or length that can't be interpreted as an
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# integer should give a TypeError ...
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with self.assertRaises(TypeError):
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slice(0.0, 10, 1).indices(5)
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with self.assertRaises(TypeError):
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slice(0, 10.0, 1).indices(5)
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with self.assertRaises(TypeError):
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slice(0, 10, 1.0).indices(5)
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with self.assertRaises(TypeError):
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slice(0, 10, 1).indices(5.0)
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# ... but it should be fine to use a custom class that provides index.
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self.assertEqual(slice(0, 10, 1).indices(5), (0, 5, 1))
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self.assertEqual(slice(MyIndexable(0), 10, 1).indices(5), (0, 5, 1))
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self.assertEqual(slice(0, MyIndexable(10), 1).indices(5), (0, 5, 1))
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self.assertEqual(slice(0, 10, MyIndexable(1)).indices(5), (0, 5, 1))
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self.assertEqual(slice(0, 10, 1).indices(MyIndexable(5)), (0, 5, 1))
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def test_setslice_without_getslice(self):
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tmp = []
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class X(object):
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def __setitem__(self, i, k):
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tmp.append((i, k))
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x = X()
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x[1:2] = 42
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self.assertEqual(tmp, [(slice(1, 2), 42)])
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def test_pickle(self):
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s = slice(10, 20, 3)
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for protocol in (0,1,2):
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t = loads(dumps(s, protocol))
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self.assertEqual(s, t)
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self.assertEqual(s.indices(15), t.indices(15))
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self.assertNotEqual(id(s), id(t))
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def test_cycle(self):
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class myobj(): pass
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o = myobj()
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o.s = slice(o)
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w = weakref.ref(o)
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o = None
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support.gc_collect()
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self.assertIsNone(w())
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if __name__ == "__main__":
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unittest.main()
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