[New-bugs-announce] [issue21949] Document the Py_SIZE() macro.

[Gregory P. Smith]

New submission from Gregory P. Smith:

The Py_SIZE() macro is not documented.  It should be.  It is very useful along with PyList_New(positive_number) after using PyList_SET_ITEM() to fill in up to the first positive_number elements of a list object in the most optimal manner by avoiding numerous redundant array resizes and error checks along the away.

The Py_SIZE() macro was introduced (in 2.6 I believe) and is specifically intended for use as an lvalue (see http://bugs.python.org/issue1724 to confirm that).  It currently has uses in several places in CPython's core and modules as well as within some third party extension modules and tools such as Cython).

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assignee: docs at python
components: Documentation
keywords: easy
messages: 222633
nosy: docs at python, gregory.p.smith
priority: normal
severity: normal
status: open
title: Document the Py_SIZE() macro.
type: performance
versions: Python 2.7, Python 3.4, Python 3.5

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<http://bugs.python.org/issue21949>
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