From: Raymond Hettinger <rhettinger@users.noreply.github.com>
Date: Tue, 12 Sep 2023 02:04:28 +0000 (+0200)
Subject: Fix iter_index() to work with lists which do not support stop=None. (gh-109306)
X-Git-Tag: v3.13.0a1~478
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=f2a55fecd063244a5fd09a38f673f0781f8802d1;p=thirdparty%2FPython%2Fcpython.git

Fix iter_index() to work with lists which do not support stop=None. (gh-109306)
---

diff --git a/Doc/library/itertools.rst b/Doc/library/itertools.rst
index 3cfc2602fe06..5e187aea441b 100644
--- a/Doc/library/itertools.rst
+++ b/Doc/library/itertools.rst
@@ -877,6 +877,7 @@ which incur interpreter overhead.
                    yield i
        else:
            # Fast path for sequences
+           stop = len(iterable) if stop is None else stop
            i = start - 1
            try:
                while True:
@@ -1345,6 +1346,16 @@ The following recipes have a more mathematical flavor:
     Traceback (most recent call last):
     ...
     ValueError
+    >>> # Verify that both paths can find identical NaN values
+    >>> x = float('NaN')
+    >>> y = float('NaN')
+    >>> list(iter_index([0, x, x, y, 0], x))
+    [1, 2]
+    >>> list(iter_index(iter([0, x, x, y, 0]), x))
+    [1, 2]
+    >>> # Test list input. Lists do not support None for the stop argument
+    >>> list(iter_index(list('AABCADEAF'), 'A'))
+    [0, 1, 4, 7]
 
     >>> list(sieve(30))
     [2, 3, 5, 7, 11, 13, 17, 19, 23, 29]