Hello Fedora!
In Python Maint, we sat down and we came up with several ideas how to minimize
the filesystem footprint of Python. Unfortunately, the result is horribly long,
sorry about that.
Please, share your feedback, additional solutions, comments etc.
Version with formatting and pictures is available at:
https://github.com/hroncok/python-minimization/blob/master/document.md
Enclosing here for better in-line responses:
# Python minimization in Fedora
> While Fedora is well suited for traditional physical/virtual workstations and
servers, it is often overlooked for use cases beyond traditional installs.
>
> Some modern types of deployments — such as IoT and containers — are quite
sensitive to size. For IoT that's usually slow data connections (for
updates/management) and for cloud and containers it’s the massive scale.
-- the preamble of the [Fedora Minimization
Objective](https://docs.fedoraproject.org/en-US/minimization/)
One of the biggest things in Fedora is Python. Because [Fedora loves
Python](https://fedoralovespython.org/) and because the package manager for
Fedora packages -- dnf -- happens to be written in Python, the Python
interpreter and its standard library comes pre-installed on many (if not all)
Fedora systems and is often not possible to remove it without destroying the
system completely or making it unmanageable.
Python comes with [Batteries
Included](https://en.wikipedia.org/wiki/Batteries_Included) -- the standard
library is quite big. While pleasant for the programmers, this comes with a
large filesystem footprint not entirely desired in Fedora. In this document, we
will analyze the footprint and offer several minimization solutions/ideas with
their challenges, pros (MiB saved) and cons. It is a list of ideas; **we're not
promising to do any of this**.
**Goal:**
1. Significantly lower the filesystem footprint of the mandatory Python
installation in Fedora.
**Non-goals:**
1. We don't aim to lower the filesystem footprint of all Python installations
in Fedora -- the default may remain big, if there is an opt-out mechanism.
2. We don't aim to lower the filesystem footprint of all Fedora Python RPM
packages, just the `python3` package and its subpackages -- the interpreter and
the standard library.
However, if any non-goal becomes a side effect of the solution of our goal,
good.
**Constraints:**
1. Do not break Python users' expectations. As an example, we don't strip
Python standard library to the bare minimum and still call it Python.
2. Do not break Fedora users' expectations. As an example, we don't break the
ability to hot patch Python files on a live system by default.
3. Do not break Fedora packagers' expectations. As an example, we don't
[require "system tools" to use a custom Python
entrypoint](https://fedoraproject.org/wiki/Changes/System_Python), such as
`/usr/libexec/platform-python` or `/usr/libexec/system-python`.
4. Do not significantly increase the filesystem footprint of the default
Python installation. As an example, we don't package [two separate versions (and
stacks) of Python](https://fedoraproject.org/wiki/Changes/Platform_Python_Stack)
-- one minimal for dnf (or Ansible) and another "normal" for the users.
5. Do not diverge from upstream significantly (but we can drive upstream
change). As an example, we don't reinvent the import machinery of Python
downstream only, but we might do it in upstream and even [use Fedora to pioneer
the change](https://fedoraproject.org/wiki/Changes/python3_c.utf-8_locale).
The listed constraints are not absolute. We will mention in each solution,
whether we feel that some constraints are violated, but that doesn't mean we
shall outright discard the solution.
## How large is Python, actually
tl;dr Python 3.8.1 in Fedora has 111 MiB (approximately 77 3.5" floppy disks),
but we only **install 37.5 MiB by default** (26 floppy disks).
*77 3.5" floppy disks, courtesy of Dana Walker. Imagine one of them is faulty.*
(All numbers are real installed disk sizes based on the `python38` package
installed on Fedora 31, x86_64. The split into subpackages is based on the
`python3` package from Fedora 32. Slight differences between Fedora 31 and 32 or
between various architectures are irrelevant here, we aim for a long term
minimization. See the [source of the numbers][source].)
In Fedora we split the Python interpreter into various RPM subpackages, some of
them are optional. This is what you get all the time:
- `python3` contains `/usr/bin/python3` and friends; has 21 KiB.
- `python3-libs` contains `/usr/lib64/libpython3.8.so.1.0` and the majority of
the standard library, is required by `python3`; has 37.5 MiB.
And this is what you get optionally:
- `python3-devel` contains the "development files" and makes it possible to
compile extension
