From 93a687a3731caf9b27be0cd021b0337010441366 Mon Sep 17 00:00:00 2001 From: Raymond Hettinger Date: Tue, 12 Mar 2024 21:33:42 -0500 Subject: [PATCH] Minor clarity improvement for the iter_index() recipe. Also add value subsequence tests. (gh-116696) --- Doc/library/itertools.rst | 25 +++++++++++++++++++++---- 1 file changed, 21 insertions(+), 4 deletions(-) diff --git a/Doc/library/itertools.rst b/Doc/library/itertools.rst index debb4138888..36e555d37d4 100644 --- a/Doc/library/itertools.rst +++ b/Doc/library/itertools.rst @@ -902,18 +902,19 @@ which incur interpreter overhead. # iter_index('AABCADEAF', 'A') --> 0 1 4 7 seq_index = getattr(iterable, 'index', None) if seq_index is None: - # Slow path for general iterables + # Path for general iterables it = islice(iterable, start, stop) for i, element in enumerate(it, start): if element is value or element == value: yield i else: - # Fast path for sequences + # Path for sequences with an index() method stop = len(iterable) if stop is None else stop - i = start - 1 + i = start try: while True: - yield (i := seq_index(value, i+1, stop)) + yield (i := seq_index(value, i, stop)) + i += 1 except ValueError: pass @@ -1412,6 +1413,22 @@ The following recipes have a more mathematical flavor: >>> ''.join(input_iterator) 'DEAF' + >>> # Verify that the target value can be a sequence. + >>> seq = [[10, 20], [30, 40], 30, 40, [30, 40], 50] + >>> target = [30, 40] + >>> list(iter_index(seq, target)) + [1, 4] + + >>> # Verify faithfulness to type specific index() method behaviors. + >>> # For example, bytes and str perform subsequence searches + >>> # that do not match the general behavior specified + >>> # in collections.abc.Sequence.index(). + >>> seq = 'abracadabra' + >>> target = 'ab' + >>> list(iter_index(seq, target)) + [0, 7] + + >>> list(sieve(30)) [2, 3, 5, 7, 11, 13, 17, 19, 23, 29] >>> small_primes = [2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97]