diff options
| -rw-r--r-- | Doc/library/collections.abc.rst | 14 | ||||
| -rw-r--r-- | Lib/_collections_abc.py | 20 | ||||
| -rw-r--r-- | Lib/test/test_collections.py | 35 | ||||
| -rw-r--r-- | Misc/ACKS | 1 | ||||
| -rw-r--r-- | Misc/NEWS | 4 |
5 files changed, 69 insertions, 5 deletions
diff --git a/Doc/library/collections.abc.rst b/Doc/library/collections.abc.rst index 28ba430142..0039bb2511 100644 --- a/Doc/library/collections.abc.rst +++ b/Doc/library/collections.abc.rst @@ -121,6 +121,20 @@ ABC Inherits from Abstract Methods Mixin ABCs for read-only and mutable :term:`sequences <sequence>`. + Implementation note: Some of the mixin methods, such as + :meth:`__iter__`, :meth:`__reversed__` and :meth:`index`, make + repeated calls to the underlying :meth:`__getitem__` method. + Consequently, if :meth:`__getitem__` is implemented with constant + access speed, the mixin methods will have linear performance; + however, if the underlying method is linear (as it would be with a + linked list), the mixins will have quadratic performance and will + likely need to be overridden. + + .. versionchanged:: 3.5 + The index() method added support for *stop* and *start* + arguments. + + .. class:: Set MutableSet diff --git a/Lib/_collections_abc.py b/Lib/_collections_abc.py index 2f83543124..0ca7debddb 100644 --- a/Lib/_collections_abc.py +++ b/Lib/_collections_abc.py @@ -825,13 +825,23 @@ class Sequence(Sized, Iterable, Container): for i in reversed(range(len(self))): yield self[i] - def index(self, value): - '''S.index(value) -> integer -- return first index of value. + def index(self, value, start=0, stop=None): + '''S.index(value, [start, [stop]]) -> integer -- return first index of value. Raises ValueError if the value is not present. ''' - for i, v in enumerate(self): - if v == value: - return i + if start is not None and start < 0: + start = max(len(self) + start, 0) + if stop is not None and stop < 0: + stop += len(self) + + i = start + while stop is None or i < stop: + try: + if self[i] == value: + return i + except IndexError: + break + i += 1 raise ValueError def count(self, value): diff --git a/Lib/test/test_collections.py b/Lib/test/test_collections.py index a15651fd7d..ec86466779 100644 --- a/Lib/test/test_collections.py +++ b/Lib/test/test_collections.py @@ -1227,6 +1227,41 @@ class TestCollectionABCs(ABCTestCase): self.validate_abstract_methods(Sequence, '__contains__', '__iter__', '__len__', '__getitem__') + def test_Sequence_mixins(self): + class SequenceSubclass(Sequence): + def __init__(self, seq=()): + self.seq = seq + + def __getitem__(self, index): + return self.seq[index] + + def __len__(self): + return len(self.seq) + + # Compare Sequence.index() behavior to (list|str).index() behavior + def assert_index_same(seq1, seq2, index_args): + try: + expected = seq1.index(*index_args) + except ValueError: + with self.assertRaises(ValueError): + seq2.index(*index_args) + else: + actual = seq2.index(*index_args) + self.assertEqual( + actual, expected, '%r.index%s' % (seq1, index_args)) + + for ty in list, str: + nativeseq = ty('abracadabra') + indexes = [-10000, -9999] + list(range(-3, len(nativeseq) + 3)) + seqseq = SequenceSubclass(nativeseq) + for letter in set(nativeseq) | {'z'}: + assert_index_same(nativeseq, seqseq, (letter,)) + for start in range(-3, len(nativeseq) + 3): + assert_index_same(nativeseq, seqseq, (letter, start)) + for stop in range(-3, len(nativeseq) + 3): + assert_index_same( + nativeseq, seqseq, (letter, start, stop)) + def test_ByteString(self): for sample in [bytes, bytearray]: self.assertIsInstance(sample(), ByteString) @@ -660,6 +660,7 @@ Bill Janssen Thomas Jarosch Juhana Jauhiainen Rajagopalasarma Jayakrishnan +Devin Jeanpierre Zbigniew Jędrzejewski-Szmek Julien Jehannet Muhammad Jehanzeb @@ -73,6 +73,10 @@ Library - Issue #23973: PEP 484: Add the typing module. +- Issue #23086: The collections.abc.Sequence() abstract base class added + *start* and *stop* parameters to the index() mixin. + Patch by Devin Jeanpierre. + - Issue #20035: Replaced the ``tkinter._fix`` module used for setting up the Tcl/Tk environment on Windows with a private function in the ``_tkinter`` module that makes no permanent changes to the environment. |