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diff --git a/doc/src/sgml/html/plpython-python23.html b/doc/src/sgml/html/plpython-python23.html new file mode 100644 index 0000000..61d7b8c --- /dev/null +++ b/doc/src/sgml/html/plpython-python23.html @@ -0,0 +1,87 @@ +<?xml version="1.0" encoding="UTF-8" standalone="no"?> +<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>45.1. Python 2 vs. Python 3</title><link rel="stylesheet" type="text/css" href="stylesheet.css" /><link rev="made" href="pgsql-docs@lists.postgresql.org" /><meta name="generator" content="DocBook XSL Stylesheets V1.79.1" /><link rel="prev" href="plpython.html" title="Chapter 45. PL/Python — Python Procedural Language" /><link rel="next" href="plpython-funcs.html" title="45.2. PL/Python Functions" /></head><body id="docContent" class="container-fluid col-10"><div xmlns="http://www.w3.org/TR/xhtml1/transitional" class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="5" align="center">45.1. Python 2 vs. Python 3</th></tr><tr><td width="10%" align="left"><a accesskey="p" href="plpython.html" title="Chapter 45. PL/Python — Python Procedural Language">Prev</a> </td><td width="10%" align="left"><a accesskey="u" href="plpython.html" title="Chapter 45. PL/Python — Python Procedural Language">Up</a></td><th width="60%" align="center">Chapter 45. PL/Python — Python Procedural Language</th><td width="10%" align="right"><a accesskey="h" href="index.html" title="PostgreSQL 13.4 Documentation">Home</a></td><td width="10%" align="right"> <a accesskey="n" href="plpython-funcs.html" title="45.2. PL/Python Functions">Next</a></td></tr></table><hr></hr></div><div class="sect1" id="PLPYTHON-PYTHON23"><div class="titlepage"><div><div><h2 class="title" style="clear: both">45.1. Python 2 vs. Python 3</h2></div></div></div><p> + PL/Python supports both the Python 2 and Python 3 language + variants. (The PostgreSQL installation instructions might contain + more precise information about the exact supported minor versions + of Python.) Because the Python 2 and Python 3 language variants + are incompatible in some important aspects, the following naming + and transitioning scheme is used by PL/Python to avoid mixing them: + + </p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p> + The PostgreSQL language named <code class="literal">plpython2u</code> + implements PL/Python based on the Python 2 language variant. + </p></li><li class="listitem"><p> + The PostgreSQL language named <code class="literal">plpython3u</code> + implements PL/Python based on the Python 3 language variant. + </p></li><li class="listitem"><p> + The language named <code class="literal">plpythonu</code> implements + PL/Python based on the default Python language variant, which is + currently Python 2. (This default is independent of what any + local Python installations might consider to be + their <span class="quote">“<span class="quote">default</span>”</span>, for example, + what <code class="filename">/usr/bin/python</code> might be.) The + default will probably be changed to Python 3 in a distant future + release of PostgreSQL, depending on the progress of the + migration to Python 3 in the Python community. + </p></li></ul></div><p> + + This scheme is analogous to the recommendations in <a class="ulink" href="https://www.python.org/dev/peps/pep-0394/" target="_top">PEP 394</a> regarding the + naming and transitioning of the <code class="command">python</code> command. + </p><p> + It depends on the build configuration or the installed packages + whether PL/Python for Python 2 or Python 3 or both are available. + </p><div class="tip"><h3 class="title">Tip</h3><p> + The built variant depends on which Python version was found during + the installation or which version was explicitly set using + the <code class="envar">PYTHON</code> environment variable; + see <a class="xref" href="install-procedure.html" title="16.4. Installation Procedure">Section 16.4</a>. To make both variants of + PL/Python available in one installation, the source tree has to be + configured and built twice. + </p></div><p> + This results in the following usage and migration strategy: + + </p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p> + Existing users and users who are currently not interested in + Python 3 use the language name <code class="literal">plpythonu</code> and + don't have to change anything for the foreseeable future. It is + recommended to gradually <span class="quote">“<span class="quote">future-proof</span>”</span> the code + via migration to Python 2.6/2.7 to simplify the eventual + migration to Python 3. + </p><p> + In practice, many PL/Python functions will migrate to Python 3 + with few or no changes. + </p></li><li class="listitem"><p> + Users who know that they have heavily Python 2 dependent code + and don't plan to ever change it can make use of + the <code class="literal">plpython2u</code> language name. This will + continue to work into the very distant future, until Python 2 + support might be completely dropped by PostgreSQL. + </p></li><li class="listitem"><p> + Users who want to dive into Python 3 can use + the <code class="literal">plpython3u</code> language name, which will keep + working forever by today's standards. In the distant future, + when Python 3 might become the default, they might like to + remove the <span class="quote">“<span class="quote">3</span>”</span> for aesthetic reasons. + </p></li><li class="listitem"><p> + Daredevils, who want to build a Python-3-only operating system + environment, can change the contents of + <code class="literal">plpythonu</code>'s extension control and script files + to make <code class="literal">plpythonu</code> be equivalent + to <code class="literal">plpython3u</code>, keeping in mind that this + would make their installation incompatible with most of the rest + of the world. + </p></li></ul></div><p> + </p><p> + See also the + document <a class="ulink" href="https://docs.python.org/3/whatsnew/3.0.html" target="_top">What's + New In Python 3.0</a> for more information about porting to + Python 3. + </p><p> + It is not allowed to use PL/Python based on Python 2 and PL/Python + based on Python 3 in the same session, because the symbols in the + dynamic modules would clash, which could result in crashes of the + PostgreSQL server process. There is a check that prevents mixing + Python major versions in a session, which will abort the session if + a mismatch is detected. It is possible, however, to use both + PL/Python variants in the same database, from separate sessions. + </p></div><div xmlns="http://www.w3.org/TR/xhtml1/transitional" class="navfooter"><hr></hr><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="plpython.html" title="Chapter 45. PL/Python — Python Procedural Language">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="plpython.html" title="Chapter 45. PL/Python — Python Procedural Language">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="plpython-funcs.html" title="45.2. PL/Python Functions">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Chapter 45. PL/Python — Python Procedural Language </td><td width="20%" align="center"><a accesskey="h" href="index.html" title="PostgreSQL 13.4 Documentation">Home</a></td><td width="40%" align="right" valign="top"> 45.2. PL/Python Functions</td></tr></table></div></body></html>
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