| # 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() |