Support python3 executable when python is not available

[mcornella]

Many systems don't link python to python3. Debian even maintains it's wrong for their packages to expect python to work:

NOTE: Debian testing (bullseye) has removed the "python" package and the '/usr/bin/python' symlink due to the deprecation of Python 2. No packaged scripts should depend on the existence of '/usr/bin/python': if they do, that is a bug that should be reported to Debian. You can use the 'python-is-python3' or 'python-is-python2' packages to restore an appropriate '/usr/bin/python' symlink for third-party or legacy scripts.

Therefore we should support both python and python3. This can be done from Zsh with the form

${commands[python]:-python3}

but the use in file shebangs is harder to do.

It should be researched whether python3 is expected to be available in all systems, so we can just rename all python uses to python3, or if either command can be available in different systems.

Reference: #10466

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Used in plugins:

• aliases
• django
• git-prompt
• jsontools
• python
• shell-proxy (as python3)
• urltools (as python2 or python3)

[carlosala]

I think that renaming every usage from python to python3 is counterproductive. Python2 is deprecated since 2 years ago, so it's a matter of time for the command python be default in every distro/OS. We can discuss about it, I don't see an easy solution for this issue.

[tkomane]

I think that renaming every usage from python to python3 is counterproductive. Python2 is deprecated since 2 years ago, so it's a matter of time for the command python be default in every distro/OS. We can discuss about it, I don't see an easy solution for this issue.

Just dealt with this issue and I'm inclined to agree with this. In the interim it might make more sense to recommend installation of 'python-is-python3' or 'python-is-python2' packages - and maybe even prompt the installation as a fallback within the respective plugin zsh scripts, (whenever a python executable can't be detected).

[carlosala]

I agree with you! Maybe we can spawn a warning if python is missing but python3 is there. By the way, I don't really know if every system that doesn't link python with python3 has those packages.

[mcornella]

I think the solution is to rename everything to python3, as stated in #10777 (comment).

[mcornella]

@carlosala can you take care of renaming every call to python for python3? Judging from the comments, that seems like the safest bet.

[carlosala]

Yes, I planned to do it last week but many things came up😅
I'll do it before Sunday!

[mcornella]

Awesome!