Python 3.8 Application Stream is currently available with RHEL 8.2 beta. Since we support every new version of Python (3 years) that we release, we need to make sure that it's stable before bringing it to RHEL and the many hardware architectures it runs on. This is also important as customers expect technologies to be production grade. This table shows that over the years, we have officially supported more than one Python version simultaneously. You can download RHEL 8.2 beta from here. RHEL 8 was released with 2 versions of Python (2.7 and 3.6) because it's an important technology for us. We've used it ourselves for many years in building RHEL components and, among others in this industry, we had to rebuild it to 3.x (from 2.7).

FYI - new versions of Python and other components are released as Software Collections on RHEL 7, and as Application Streams on RHEL 8. The benefit of these is that the version of Python that's installed will have exactly the same packages and components for each system it's install it on. This simplifies things a lot (as you point out, it's complicated) and minimizes the "it works on my machine" issue.

In your interactive bash shell, python is resolved to python3 by an alias.

Aliases are not inherited, so the /bin/sh sub-process can't resolve it. Although you could create a symbolic link so that python resolves to python3 via the shell's inherited PATH, best practice is to specify python3 explicitly.

See this related discussion at Python in RHEL 8

Two notes: I'm not sure how your container is set. You've tagged this as both RHEL and Fedora. These are two separate distributions. I can comment on Fedora.

Firstly, yes, Python is heavily used in the GNU/Linux world. Most distros use it as one of the languages to build the system and its packages. Linux servers are the only officially recommended servers for Python, or so I've read (will edit with source later if I can find it). Python.org does have Linux downloads, but in source files, packaged in compressed tarballs. This can promote searching the distro package manager first for distro compatibility (since being in a distro's repo should mean the version was vetted); these packages are precompiled unless otherwise specified. It also means the files are distro agnostic -- no need for .DEB, .RPM...

Fedora: There isn't a Fedora version listed in the post, but at least Fedora 31 has a development version, as they call it, of Python 3.8.1 in RPM format. (Fedora 32 is slated to have Python 3.8 at the system level.) You can get it with:

Copysudo dnf install python38

Be sure not to overwrite the system variables for python or python3; this mistake can cause systemic issues of varying magnitude. Once installed, you can create a virtual environment in whichever directory you'd like with:

Copypython3.8 -m venv <venv_name>

To activate the venv, use:

Copy. <path/to/venv>/<venv_name>/bin/activate

You can set an alias or symlink for ease. When the venv is activated, Python 3.8.x will be the Python version used when the interpreter is called. You should see your venv_name in parentheses, to the left of your PS1. To deactivate, use:

Copydeactivate

The venv_name should be removed from the PS1, returning it to normal. Checking the Python version should return the system-level Python version.

If you check your Python version before and after the activation, it should be different.

Copypython3 -V

This package may or may not have been sent downstream to RHEL. If you have the package available but want the full Python stack, or if it isn't available in RHEL's baseline repos, you may need to grab the source files and unpack the tarballs.

Alternatives are checking other repos, seeing about RPMs that someone else compiled from source, or checking out flatpak (which I haven't done).

Last note: compiling from source shouldn't result in a larger Python binary. You can delete any unnecessary extras, like the original archive file used for compiling, after you've extracted what you need. The action itself will only be stored in volatile memory, not on your disk.