https://github.com/python/cpython/commit/93a687a3731caf9b27be0cd021b0337010441366
commit: 93a687a3731caf9b27be0cd021b0337010441366
branch: main
author: Raymond Hettinger <[email protected]>
committer: rhettinger <[email protected]>
date: 2024-03-12T21:33:42-05:00
summary:
Minor clarity improvement for the iter_index() recipe. Also add value
subsequence tests. (gh-116696)
files:
M Doc/library/itertools.rst
diff --git a/Doc/library/itertools.rst b/Doc/library/itertools.rst
index debb4138888e99..36e555d37d45de 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]
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