source: chapter08/python.xml@ b094e3f

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  "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  \
            --with-system-ffi    \
            --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>--with-system-ffi</parameter></term>
      <listitem>
        <para>This switch enables linking against the system version of
        <filename class='libraryfile'>libffi.so</filename>.</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>Running the tests at this point is not recommended.  The
    tests are known to hang indefinitely in the partial LFS environment.
    If desired, the tests can be rerun at the end of this chapter, or
    when Python 3 is reinstalled in BLFS.  To run the tests anyway,
    issue <command>make test</command>.</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 --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>