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"http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" [
<!ENTITY % general-entities SYSTEM "../general.ent">
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]>
<sect1 id="ch-system-Python" role="wrap">
<?dbhtml filename="Python.html"?>
<sect1info condition="script">
<productname>Python</productname>
<productnumber>&python-version;</productnumber>
<address>&python-url;</address>
</sect1info>
<title>Python-&python-version;</title>
<indexterm zone="ch-system-Python">
<primary sortas="a-Python">Python</primary>
</indexterm>
<sect2 role="package">
<title/>
<para>The Python 3 package contains the Python development environment. It
is useful for object-oriented programming, writing scripts, prototyping
large programs, and developing entire applications. Python is an interpreted
computer language.</para>
<segmentedlist>
<segtitle>&buildtime;</segtitle>
<segtitle>&diskspace;</segtitle>
<seglistitem>
<seg>&python-fin-sbu;</seg>
<seg>&python-fin-du;</seg>
</seglistitem>
</segmentedlist>
</sect2>
<sect2 role="installation">
<title>Installation of Python 3</title>
<para>Prepare Python for compilation:</para>
<screen><userinput remap="configure">./configure --prefix=/usr \
--enable-shared \
--with-system-expat \
--enable-optimizations</userinput></screen>
<variablelist>
<title>The meaning of the configure options:</title>
<varlistentry>
<term><parameter>--with-system-expat</parameter></term>
<listitem>
<para>This switch enables linking against the system version of
<application>Expat</application>.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>--enable-optimizations</parameter></term>
<listitem>
<para>This switch enables extensive, but time-consuming, optimization
steps. The interpreter is built twice; tests performed on the first
build are used to improve the optimized final version.</para>
<!-- This description was drawn from the README.rst file
in the Python-3.11.0 package. -->
</listitem>
</varlistentry>
</variablelist>
<para>Compile the package:</para>
<screen><userinput remap="make">make</userinput></screen>
<para>Some tests are known to occasionally hang indefinitely. So to test the
results, run the test suite but set a 2-minute time limit for each
test case:</para>
<screen><userinput remap="test">make test TESTOPTS="--timeout 120"</userinput></screen>
<para>For a relatively slow system you may need to increase the time
limit and 1 SBU (measured when building Binutils pass 1 with one CPU
core) should be enough. Some tests are flaky, so the test suite will
automatically re-run failed tests. If a test failed but then passed
when re-run, it should be considered as passed. One test, test_ssl,
is known to fail in the chroot environment.</para>
<para>Install the package:</para>
<screen><userinput remap="install">make install</userinput></screen>
<para>We use the <command>pip3</command> command to
install Python 3 programs and modules for all users as
<systemitem class='username'>root</systemitem> in several places in this book.
This conflicts with the Python developers' recommendation: to install packages into a
virtual environment, or into the home directory of a regular user (by running
<command>pip3</command> as this user). A multi-line warning
is triggered whenever <command>pip3</command> is issued by the
<systemitem class='username'>root</systemitem> user.</para>
<para>The main reason
for the recommendation is to avoid conflicts with the system's
package manager (<command>dpkg</command>, for example). LFS does not
have a system-wide package manager, so this is not a problem. Also,
<command>pip3</command> will check for a new version of
itself whenever it's run. Since domain name resolution is not yet configured
in the LFS chroot environment, <command>pip3</command> cannot check
for a new version of itself, and will
produce a warning. </para>
<para>After we boot the LFS system and set up a network connection,
a different warning will be issued, telling the user to update <command>pip3</command>
from a pre-built wheel on PyPI (whenever a new version is available). But LFS
considers <command>pip3</command> to be a part of Python 3, so it should not be
updated separately. Also, an update from a pre-built wheel would deviate
from our objective: to build a Linux system from source code. So the
warning about a new version of <command>pip3</command> should be ignored as
well. If you wish, you can suppress all these warnings by running the following
command, which creates a configuration file:</para>
<screen><userinput remap="install">cat > /etc/pip.conf << EOF
<literal>[global]
root-user-action = ignore
disable-pip-version-check = true</literal>
EOF
</userinput></screen>
<!--
<screen><userinput remap="install">sed -e '/def warn_if_run_as_root/a\ return' \
-i /usr/lib/python3.10/site-packages/pip/_internal/cli/req_command.py
</userinput></screen>
-->
<important>
<para>
In LFS and BLFS we normally build and install Python modules with the
<command>pip3</command> command. Please be sure that the
<command>pip3 install</command> commands in both books are
run as the &root; user (unless it's for a Python virtual environment).
Running <command>pip3 install</command> as a non-&root; user may seem
to work, but it will cause the installed module to be inaccessible
by other users.
</para>
<para>
<command>pip3 install</command> will not reinstall an already installed
module automatically. When using the <command>pip3 install</command>
command to upgrade a module (for example, from meson-0.61.3 to
meson-0.62.0), insert the option <parameter>--upgrade</parameter> into
the command line. If it's really necessary to downgrade a module, or
reinstall the same version for some reason, insert
<parameter>--force-reinstall --no-deps</parameter> into the command
line.
</para>
</important>
<para>If desired, install the preformatted documentation:</para>
<screen><userinput remap="install">install -v -dm755 /usr/share/doc/python-&python-version;/html
tar --strip-components=1 \
--no-same-owner \
--no-same-permissions \
-C /usr/share/doc/python-&python-version;/html \
-xvf ../python-&python-version;-docs-html.tar.bz2</userinput></screen>
<variablelist>
<title>The meaning of the documentation install commands:</title>
<varlistentry>
<term><option>--no-same-owner</option> and <option>--no-same-permissions</option></term>
<listitem>
<para>Ensure the installed files have the correct ownership and
permissions. Without these options, <application>tar</application>
will install the package files with the upstream creator's values.
</para>
</listitem>
</varlistentry>
</variablelist>
</sect2>
<sect2 id="contents-python" role="content">
<title>Contents of Python 3</title>
<segmentedlist>
<segtitle>Installed programs</segtitle>
<segtitle>Installed library</segtitle>
<segtitle>Installed directories</segtitle>
<seglistitem>
<seg>
2to3, idle3, pip3, pydoc3, python3, and python3-config
</seg>
<seg>
libpython&python-minor;.so and libpython3.so
</seg>
<seg>
/usr/include/python&python-minor;,
/usr/lib/python3, and
/usr/share/doc/python-&python-version;
</seg>
</seglistitem>
</segmentedlist>
<variablelist>
<bridgehead renderas="sect3">Short Descriptions</bridgehead>
<?dbfo list-presentation="list"?>
<?dbhtml list-presentation="table"?>
<varlistentry id="python-2to3">
<term><command>2to3</command></term>
<listitem>
<para>
is a <application>Python</application> program that reads
<application>Python 2.x</application> source code and applies a
series of fixes to transform it into
valid <application>Python 3.x</application> code
</para>
<indexterm zone="ch-system-Python">
<primary sortas="b-2to3">2to3</primary>
</indexterm>
</listitem>
</varlistentry>
<varlistentry id="idle3">
<term><command>idle3</command></term>
<listitem>
<para>
is a wrapper script that opens a <application>Python</application>
aware GUI editor. For this script to run, you must have installed
<application>Tk</application> before Python, so that the Tkinter
Python module is built.
</para>
<indexterm zone="ch-system-Python">
<primary sortas="b-idle3">idle3</primary>
</indexterm>
</listitem>
</varlistentry>
<varlistentry id="pip3">
<term><command>pip3</command></term>
<listitem>
<para>
The package installer for Python. You can use pip to install
packages from Python Package Index and other indexes.
</para>
<indexterm zone="ch-system-Python">
<primary sortas="b-pip3">pip3</primary>
</indexterm>
</listitem>
</varlistentry>
<varlistentry id="pydoc3">
<term><command>pydoc3</command></term>
<listitem>
<para>
is the <application>Python</application> documentation tool
</para>
<indexterm zone="ch-system-Python">
<primary sortas="b-pydoc3">pydoc3</primary>
</indexterm>
</listitem>
</varlistentry>
<varlistentry id="python3">
<term><command>python3</command></term>
<listitem>
<para>
is the interpreter for Python, an interpreted, interactive,
object-oriented programming language
</para>
<indexterm zone="ch-system-Python">
<primary sortas="b-python3">python3</primary>
</indexterm>
</listitem>
</varlistentry>
</variablelist>
</sect2>
</sect1>