On 08/29/2018 09:05 PM, Michael F. Stemper wrote:
I can certainly see a use case for user-specific versions of
modules, and even user-specific presence of modules. For
instance, at school, different researchers might need to have
specific modules for their work. Possibly one person is doing
something with a 3PP built on a specific version of a module
that would be incompatible with a later version.
However, why would I want this on my home servers? It seems to
me that having different versions for different people on my
home network would rapidly become a maintenance problem.
I'm the only one who writes code here. If I was to tell somebody,
"Hey, look at what I wrote," it'd be nice if their environment
had all of the same stuff as mine.
I'd stick with distribution packages as far as possible if I were you.
The nice thing about installing custom packages from PyPI in ~/.local
only is that while I /might/ mess up my own environment, I'm not risking
the functionality of system components/daemons/etc. running as root. But
I'm no sysadmin.
(I realize that you're the messenger, not the designer. It seems
as if my beef is probably with Canonical or even Debian.)
Oh no, the problem exists on every Linux distro, and I assume Ruby, Perl
and R users have the same kinds of problems. Heck, I've had similar
problems with LaTeX/TeXlive...
Also, PLEASE use Python 3. Still using Python 2 today is like still
using Windows XP in early 2013.
I'm using the default version for the current release of my
OS (Ubuntu 16.04 LTS):
user@host$ ls -lrtd python python?
lrwxrwxrwx 1 root root 9 Nov 22 2016 python3 -> python3.5
lrwxrwxrwx 1 root root 9 Nov 23 2017 python2 -> python2.7
lrwxrwxrwx 1 root root 9 Nov 23 2017 python -> python2.7
user@host$
My understanding is that when I get around to upgrading to 18.04 LTS,
python3 will be the default.
Since I don't hard-code a version in any of my programs, but simply
write "#!/usr/bin/python", all of my programs will automatically change
to the new version then.
No, actually.
As I understand it, Ubuntu 18.04 LTS uses python2 a lot less, and I
don't think it's included in the default install. However, it's still in
main, the name of the package is still "python", and it's still required
by some common software... (including the recommended personal backup
tool, duplicity :-/)
In any case, as per PEP 394, /usr/bin/python continues to point to
Python 2.7 (if installed), it it will likely remain that way for the
foreseeable future. (including, presumably, Ubuntu 20.04 LTS)
PEP 394: https://www.python.org/dev/peps/pep-0394/
If I was to change all of my programs to say "#!/usr/bin/python3", I'd
have a slight head-start. However, then I'd need to change them all
again when python 4 came out. And python 5.
I prefer to maintain version independence, or at least to avoid
implementing version dependence.
You should know that there were some (deliberate) incompatible changes
(vastly for the better) in Python 3.0 (almost ten years ago). It's
normally easy to port your code, and not too hard to write code that
runs on both Python 2 and Python 3 if required, but in any case you have
to do this consciously, and code written for Python 2 will not in
general work unmodified on Python 3.
At least for new scripts, just use #!/usr/bin/python3 or #!/usr/bin/env
python3.
As for the "Python 4 problem" – at the moment nobody knows whether there
will even /be/ a Python 4. Maybe Python 4.0 will be the version after
3.9 (doubtful IMHO). Maybe it'll come later. Maybe it never will. It
certainly won't include any major breaking changes, and considering PEP
394, I could imagine that when the time comes we will see
/usr/bin/python3 pointing to /usr/bin/python4.0 (as silly as that sounds).
-- Thomas
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