diff --git a/Lib/test/test_slice.py b/Lib/test/test_slice.py new file mode 100644 index 000000000..4ae4142c6 --- /dev/null +++ b/Lib/test/test_slice.py @@ -0,0 +1,255 @@ +# tests for slice objects; in particular the indices method. + +import itertools +import operator +import sys +import unittest +import weakref + +from pickle import loads, dumps +from test import support + + +def evaluate_slice_index(arg): + """ + Helper function to convert a slice argument to an integer, and raise + TypeError with a suitable message on failure. + + """ + if hasattr(arg, '__index__'): + return operator.index(arg) + else: + raise TypeError( + "slice indices must be integers or " + "None or have an __index__ method") + +def slice_indices(slice, length): + """ + Reference implementation for the slice.indices method. + + """ + # Compute step and length as integers. + length = operator.index(length) + step = 1 if slice.step is None else evaluate_slice_index(slice.step) + + # Raise ValueError for negative length or zero step. + if length < 0: + raise ValueError("length should not be negative") + if step == 0: + raise ValueError("slice step cannot be zero") + + # Find lower and upper bounds for start and stop. + lower = -1 if step < 0 else 0 + upper = length - 1 if step < 0 else length + + # Compute start. + if slice.start is None: + start = upper if step < 0 else lower + else: + start = evaluate_slice_index(slice.start) + start = max(start + length, lower) if start < 0 else min(start, upper) + + # Compute stop. + if slice.stop is None: + stop = lower if step < 0 else upper + else: + stop = evaluate_slice_index(slice.stop) + stop = max(stop + length, lower) if stop < 0 else min(stop, upper) + + return start, stop, step + + +# Class providing an __index__ method. Used for testing slice.indices. + +class MyIndexable(object): + def __init__(self, value): + self.value = value + + def __index__(self): + return self.value + + +class SliceTest(unittest.TestCase): + + def test_constructor(self): + self.assertRaises(TypeError, slice) + self.assertRaises(TypeError, slice, 1, 2, 3, 4) + + def test_repr(self): + self.assertEqual(repr(slice(1, 2, 3)), "slice(1, 2, 3)") + + def test_hash(self): + # Verify clearing of SF bug #800796 + self.assertRaises(TypeError, hash, slice(5)) + with self.assertRaises(TypeError): + slice(5).__hash__() + + def test_cmp(self): + s1 = slice(1, 2, 3) + s2 = slice(1, 2, 3) + s3 = slice(1, 2, 4) + self.assertEqual(s1, s2) + self.assertNotEqual(s1, s3) + self.assertNotEqual(s1, None) + self.assertNotEqual(s1, (1, 2, 3)) + self.assertNotEqual(s1, "") + + class Exc(Exception): + pass + + class BadCmp(object): + def __eq__(self, other): + raise Exc + + s1 = slice(BadCmp()) + s2 = slice(BadCmp()) + self.assertEqual(s1, s1) + self.assertRaises(Exc, lambda: s1 == s2) + + s1 = slice(1, BadCmp()) + s2 = slice(1, BadCmp()) + self.assertEqual(s1, s1) + self.assertRaises(Exc, lambda: s1 == s2) + + s1 = slice(1, 2, BadCmp()) + s2 = slice(1, 2, BadCmp()) + self.assertEqual(s1, s1) + self.assertRaises(Exc, lambda: s1 == s2) + + def test_members(self): + s = slice(1) + self.assertEqual(s.start, None) + self.assertEqual(s.stop, 1) + self.assertEqual(s.step, None) + + s = slice(1, 2) + self.assertEqual(s.start, 1) + self.assertEqual(s.stop, 2) + self.assertEqual(s.step, None) + + s = slice(1, 2, 3) + self.assertEqual(s.start, 1) + self.assertEqual(s.stop, 2) + self.assertEqual(s.step, 3) + + class AnyClass: + pass + + obj = AnyClass() + s = slice(obj) + self.assertTrue(s.stop is obj) + + def check_indices(self, slice, length): + try: + actual = slice.indices(length) + except ValueError: + actual = "valueerror" + try: + expected = slice_indices(slice, length) + except ValueError: + expected = "valueerror" + self.assertEqual(actual, expected) + + if length >= 0 and slice.step != 0: + actual = range(*slice.indices(length)) + expected = range(length)[slice] + self.assertEqual(actual, expected) + + def test_indices(self): + self.assertEqual(slice(None ).indices(10), (0, 10, 1)) + self.assertEqual(slice(None, None, 2).indices(10), (0, 10, 2)) + self.assertEqual(slice(1, None, 2).indices(10), (1, 10, 2)) + self.assertEqual(slice(None, None, -1).indices(10), (9, -1, -1)) + self.assertEqual(slice(None, None, -2).indices(10), (9, -1, -2)) + self.assertEqual(slice(3, None, -2).indices(10), (3, -1, -2)) + # issue 3004 tests + self.assertEqual(slice(None, -9).indices(10), (0, 1, 1)) + self.assertEqual(slice(None, -10).indices(10), (0, 0, 1)) + self.assertEqual(slice(None, -11).indices(10), (0, 0, 1)) + self.assertEqual(slice(None, -10, -1).indices(10), (9, 0, -1)) + self.assertEqual(slice(None, -11, -1).indices(10), (9, -1, -1)) + self.assertEqual(slice(None, -12, -1).indices(10), (9, -1, -1)) + self.assertEqual(slice(None, 9).indices(10), (0, 9, 1)) + self.assertEqual(slice(None, 10).indices(10), (0, 10, 1)) + self.assertEqual(slice(None, 11).indices(10), (0, 10, 1)) + self.assertEqual(slice(None, 8, -1).indices(10), (9, 8, -1)) + self.assertEqual(slice(None, 9, -1).indices(10), (9, 9, -1)) + self.assertEqual(slice(None, 10, -1).indices(10), (9, 9, -1)) + + self.assertEqual( + slice(-100, 100 ).indices(10), + slice(None).indices(10) + ) + self.assertEqual( + slice(100, -100, -1).indices(10), + slice(None, None, -1).indices(10) + ) + self.assertEqual(slice(-100, 100, 2).indices(10), (0, 10, 2)) + + self.assertEqual(list(range(10))[::sys.maxsize - 1], [0]) + + # Check a variety of start, stop, step and length values, including + # values exceeding sys.maxsize (see issue #14794). + vals = [None, -2**100, -2**30, -53, -7, -1, 0, 1, 7, 53, 2**30, 2**100] + lengths = [0, 1, 7, 53, 2**30, 2**100] + for slice_args in itertools.product(vals, repeat=3): + s = slice(*slice_args) + for length in lengths: + self.check_indices(s, length) + self.check_indices(slice(0, 10, 1), -3) + + # Negative length should raise ValueError + with self.assertRaises(ValueError): + slice(None).indices(-1) + + # Zero step should raise ValueError + with self.assertRaises(ValueError): + slice(0, 10, 0).indices(5) + + # Using a start, stop or step or length that can't be interpreted as an + # integer should give a TypeError ... + with self.assertRaises(TypeError): + slice(0.0, 10, 1).indices(5) + with self.assertRaises(TypeError): + slice(0, 10.0, 1).indices(5) + with self.assertRaises(TypeError): + slice(0, 10, 1.0).indices(5) + with self.assertRaises(TypeError): + slice(0, 10, 1).indices(5.0) + + # ... but it should be fine to use a custom class that provides index. + self.assertEqual(slice(0, 10, 1).indices(5), (0, 5, 1)) + self.assertEqual(slice(MyIndexable(0), 10, 1).indices(5), (0, 5, 1)) + self.assertEqual(slice(0, MyIndexable(10), 1).indices(5), (0, 5, 1)) + self.assertEqual(slice(0, 10, MyIndexable(1)).indices(5), (0, 5, 1)) + self.assertEqual(slice(0, 10, 1).indices(MyIndexable(5)), (0, 5, 1)) + + def test_setslice_without_getslice(self): + tmp = [] + class X(object): + def __setitem__(self, i, k): + tmp.append((i, k)) + + x = X() + x[1:2] = 42 + self.assertEqual(tmp, [(slice(1, 2), 42)]) + + def test_pickle(self): + s = slice(10, 20, 3) + for protocol in (0,1,2): + t = loads(dumps(s, protocol)) + self.assertEqual(s, t) + self.assertEqual(s.indices(15), t.indices(15)) + self.assertNotEqual(id(s), id(t)) + + def test_cycle(self): + class myobj(): pass + o = myobj() + o.s = slice(o) + w = weakref.ref(o) + o = None + support.gc_collect() + self.assertIsNone(w()) + +if __name__ == "__main__": + unittest.main()