I'd like to revive the discussion on best practices for installing Python applications which are version-dependent. If we can come up with some general guidelines we can mostly agree on, I'll update the AppStyleGuide wiki page.
Of course, most Python applications which expose a cli don't need to expose
different /usr/bin scripts based on the Python version. They run on Python 2
or Python 3 and don't care about the minor version number. So we just install
them as /usr/bin/whatever with a #! of /usr/bin/python or /usr/bin/python3.
Happy happy, joy joy.
Some cli's do care though, e.g. nose. In those cases, I think common practice
seems to be the following:
* Ensure that the script can be invoked via -m flag. Thus
$python -m myscript
will always work and do the right thing, when invoked with whatever $python
you care about (e.g. python2.7 or python3, or python3.3).
* Expose /usr/bin/foo with a shebang line of #!/usr/bin/python
* Expose /usr/bin/foo-3 with a shebang line of #!/usr/bin/python3
- Question: dash or no dash in the script name? I think we've seen both
and I don't have a strong opinion, although when the script itself has a
version number embedded in it, it pretty much has to have a dash between
that and the Python version. E.g. /usr/bin/nose2-3.3
* If the minor version number matters, include a /usr/bin/foo-X.Y with a
shebang line /usr/bin/pythonX.Y.
- Question: we don't seem to be entirely consistent about this. Sometimes
the shebang line for /usr/bin/foo-X.Y is /usr/bin/pythonX (where X can be
the empty string for Python 2).
- Question should /usr/bin/foo-X.Y ever be a symlink to /usr/bin/foo-X?
Those seem to be the rules we're following. I'm not entirely sure whether
pybuild and friends helps with any of this or stays agnostic.
Am I missing anything? Can anybody improve on those rules above? Should we
just adopt them as our standard recommendation (not requirement)?
Cheers,
-Barry
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