[Python-checkins] Emphasize the need to always call PySequence_Fast. (GH-11140)
Benjamin Peterson
webhook-mailer at python.org
Thu Sep 12 12:19:10 EDT 2019
https://github.com/python/cpython/commit/57b7dbc46e71269d855e644d30826d33eedee2a1
commit: 57b7dbc46e71269d855e644d30826d33eedee2a1
branch: master
author: Matti Picus <matti.picus at gmail.com>
committer: Benjamin Peterson <benjamin at python.org>
date: 2019-09-12T17:19:06+01:00
summary:
Emphasize the need to always call PySequence_Fast. (GH-11140)
files:
M Doc/c-api/sequence.rst
diff --git a/Doc/c-api/sequence.rst b/Doc/c-api/sequence.rst
index d11a2dde54dd..fe1c252ce9ba 100644
--- a/Doc/c-api/sequence.rst
+++ b/Doc/c-api/sequence.rst
@@ -130,10 +130,17 @@ Sequence Protocol
.. c:function:: PyObject* PySequence_Fast(PyObject *o, const char *m)
- Return the sequence or iterable *o* as a list, unless it is already a tuple or list, in
- which case *o* is returned. Use :c:func:`PySequence_Fast_GET_ITEM` to access
- the members of the result. Returns *NULL* on failure. If the object is not
- a sequence or iterable, raises :exc:`TypeError` with *m* as the message text.
+ Return the sequence or iterable *o* as an object usable by the other
+ ``PySequence_Fast*`` family of functions. If the object is not a sequence or
+ iterable, raises :exc:`TypeError` with *m* as the message text. Returns
+ *NULL* on failure.
+
+ The ``PySequence_Fast*`` functions are thus named because they assume
+ *o* is a :c:type:`PyTupleObject` or a :c:type:`PyListObject` and access
+ the data fields of *o* directly.
+
+ As a CPython implementation detail, if *o* is already a sequence or list, it
+ will be returned.
.. c:function:: Py_ssize_t PySequence_Fast_GET_SIZE(PyObject *o)
@@ -141,8 +148,8 @@ Sequence Protocol
Returns the length of *o*, assuming that *o* was returned by
:c:func:`PySequence_Fast` and that *o* is not *NULL*. The size can also be
gotten by calling :c:func:`PySequence_Size` on *o*, but
- :c:func:`PySequence_Fast_GET_SIZE` is faster because it can assume *o* is a list
- or tuple.
+ :c:func:`PySequence_Fast_GET_SIZE` is faster because it can assume *o* is a
+ list or tuple.
.. c:function:: PyObject* PySequence_Fast_GET_ITEM(PyObject *o, Py_ssize_t i)
@@ -163,7 +170,7 @@ Sequence Protocol
.. c:function:: PyObject* PySequence_ITEM(PyObject *o, Py_ssize_t i)
- Return the *i*\ th element of *o* or *NULL* on failure. Macro form of
+ Return the *i*\ th element of *o* or *NULL* on failure. Faster form of
:c:func:`PySequence_GetItem` but without checking that
:c:func:`PySequence_Check` on *o* is true and without adjustment for negative
indices.
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