8.50. Python-3.10.6

#### Linux From Scratch - Version 11.2-systemd

### Chapter 8. Installing Basic System Software

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# 8.50. Python-3.10.6

The Python 3 package contains the Python development environment. It is useful for object-oriented programming, writing scripts, prototyping large programs, or developing entire applications.

Approximate build time: 3.4 SBU
Required disk space: 283 MB

## 8.50.1. Installation of Python 3

Prepare Python for compilation:

    ./configure --prefix=/usr        \
                --enable-shared      \
                --with-system-expat  \
                --with-system-ffi    \
                --enable-optimizations

The meaning of the configure options:

`--with-system-expat`

  This switch enables linking against system version of Expat.

`--with-system-ffi`

  This switch enables linking against system version of libffi.

`--enable-optimizations`

  This switch enables stable, but expensive, optimizations.

Compile the package:

    make

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 make test.

Install the package:

    make install

In several places we use the pip3 command to install Python 3 programs and modules for all users as `root`. This conflicts with the Python developers recommendation to install packages into a virtual environment or the home directory of a regular user (by running pip3 as this user). To this end, a multi-line warning is written when using pip3 as the `root` user. The main reason of this recommendation is for avoiding a conflict with the system package manager (dpkg for example), but LFS does not have a system-wide package manager so this is not a problem. And, pip3 will attempt to check for a new version of itself whenever it's run. As domain name resolving is not configured yet in LFS chroot environment, it will fail to check for a new version and produce a warning. Once we boot the LFS system and set up network connection, it will then produce a warning telling the user to update it from a pre-built wheel on PyPI if any new version is available. But LFS consider pip3 a part of Python 3 so it should not be updated separately, and an update from a pre-built wheel will deviate from our purpose to build a Linux system from source code. So the warning for a new pip3 version should be ignored as well. If desired, suppress these warnings by running the following commands:

    cat > /etc/pip.conf << EOF
    [global]
    root-user-action = ignore
    disable-pip-version-check = true
    EOF

### Important

In LFS and BLFS we normally build and install Python modules with the pip3 command. Please take care that the pip3 install commands in both the books should be run as the `root` user unless it's for a Python virtual environment. Running a pip3 install as a non-`root` user may seem to work fine, but it will cause the installed module to be inaccessible by other users.

pip3 install will not reinstall an already installed module by default. For using the pip3 install command to upgrade a module (for example, from meson-0.61.3 to meson-0.62.0), insert the option `--upgrade` into the command line. If it's really necessary to downgrade a module or reinstall the same version for some reason, insert `--force-reinstall --no-deps` into the command line.

If desired, install the preformatted documentation:

    install -v -dm755 /usr/share/doc/python-3.10.6/html

    tar --strip-components=1  \
        --no-same-owner       \
        --no-same-permissions \
        -C /usr/share/doc/python-3.10.6/html \
        -xvf ../python-3.10.6-docs-html.tar.bz2

The meaning of the documentation install commands:

`--no-same-owner` and `--no-same-permissions`

  Ensure the installed files have the correct ownership and permissions. Without these options, using tar will install the package files with the upstream creator's values.

## 8.50.2. Contents of Python 3

Installed Programs: 2to3, idle3, pip3, pydoc3, python3, and python3-config
Installed Library: libpython3.10.so and libpython3.so
Installed Directories: /usr/include/python3.10, /usr/lib/python3, and /usr/share/doc/python-3.10.6

### Short Descriptions

2to3 | is a Python program that reads Python 2.x source code and applies a series of fixes to transform it into valid Python 3.x code
idle3 | is a wrapper script that opens a Python aware GUI editor. For this script to run, you must have installed Tk before Python so that the Tkinter Python module is built
pip3 | The package installer for Python. You can use pip to install packages from Python Package Index and other indexes
pydoc3 | is the Python documentation tool
python3 | is an interpreted, interactive, object-oriented programming language

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