source: chapter08/python.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE sect1 PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
  "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" [
  <!ENTITY % general-entities SYSTEM "../general.ent">
  %general-entities;
]>

<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.</para>

    <para>Two tests named <filename>test_xml_etree</filename> and
    <filename>test_xml_etree_c</filename> are known to fail with expat-2.6.0
    or newer.</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 &gt; /etc/pip.conf &lt;&lt; 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 --no-same-owner \
    -xvf ../python-&python-version;-docs-html.tar.bz2
cp -R --no-preserve=mode python-&python-version;-docs-html/* \
    /usr/share/doc/python-&python-version;/html</userinput></screen>

    <variablelist>
      <title>The meaning of the documentation install commands:</title>

    <varlistentry>
      <term><option>--no-same-owner</option> (tar) and <option>--no-preserve=mode</option> (cp)</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
        and files would have restrictive permissions.
        </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>