Server 20.04 verses 16.04: python-gnuplot

[Doug Smythies]

Hi Bryce, Rafael,

Thank you for your quick replies.
Both replies were helpful.
For some of the work I do on idle, I need bare metal with minimal
services running, no VM's or LXD containers or anything really.

On 2020.01.19 17:03 Bryce Harrington wrote:
> On Sun, Jan 19, 2020 at 04:24:13PM -0800, Doug Smythies wrote:
>> I have been unable to get it working on a new 20.04 installation.
>> If I attempt to install "python-gnuplot" I get:
>
> Yes, efforts in focal development are striving to remove python2, so for
> 20.04 forward the python3-* packages are the ones to prefer.

Yes, that makes sense.

I have not followed the issues, but am of the understanding that
the transition from python 2 to 3 has not been easy.

> python3-gnuplot only has a couple dependencies; the problem appears to
> be gnuplot itself, which is pulling the whole X11 stack in.

Yes, agreed. It didn't used to do that.

>  Looking at
> the gnuplot package, it actually provides three variants:  gnuplot-x11,
> gnuplot-qt, and gnuplot-nox.

Oh.

> If you do this:
>
>  # apt-get install gnuplot-nox python3-gnuplot
>  ...
>  0 upgraded, 45 newly installed, 0 to remove and 126 not upgraded.
>  Need to get 32.7 MB of archives.
>
> it cuts down quite a bit.  Most of this appears to be fonts and file
> formats, which seems reasonable although it's probably still more than
> you actually need.

Yes, that seems to work, on a VM at least.
It will be awhile yet until I repair the real test computer and try it for real.

> Make sure your script is using python3 in its shbang:
>
>  #!/usr/bin/env python3

Oh, that seems to be very important.
I had just assumed that the existing "#!/usr/bin/python" would take care
of version control issues. Maybe it eventually will for 20.04.
Currently, I see it maps to python version 2 on a couple of computers,
but doesn't exist on a 20.04 server VM I made for this e-mail thread.

I also observe that somewhere along the way my new 20.04 server seems to
have managed to get some of python 2 installed:

lrwxrwxrwx 1 root   root           7 Oct 10 04:32  python -> python2
lrwxrwxrwx 1 root   root           9 Oct 10 04:32  python2 -> python2.7
-rwxr-xr-x 1 root   root     3706928 Oct 19 16:36  python2.7
lrwxrwxrwx 1 root   root          33 Oct 19 16:36  python2.7-config -> x86_64-linux-gnu-python2.7-config
lrwxrwxrwx 1 root   root          16 Oct 10 04:32  python2-config -> python2.7-config
-rwxr-xr-x 1 root   root         385 Jan  9 07:09  python2-futurize
-rwxr-xr-x 1 root   root         389 Jan  9 07:09  python2-pasteurize
lrwxrwxrwx 1 root   root           9 Dec  5 21:07  python3 -> python3.7
-rwxr-xr-x 2 root   root     5102648 Dec 19 01:25  python3.7
-rwxr-xr-x 2 root   root     5102648 Dec 19 01:25  python3.7m
-rwxr-xr-x 1 root   root     5441248 Nov 22 20:55  python3.8
lrwxrwxrwx 1 root   root          10 Dec  5 21:07  python3m -> python3.7m

Whereas the new VM (with no other packages installed, except as per above) has:

lrwxrwxrwx 1 root   root           9 Jan 19 14:58  python3 -> python3.7
-rwxr-xr-x 2 root   root     5102648 Dec 19 01:25  python3.7
-rwxr-xr-x 2 root   root     5102648 Dec 19 01:25  python3.7m
-rwxr-xr-x 1 root   root     5441248 Nov 22 20:55  python3.8
lrwxrwxrwx 1 root   root          10 Jan 19 14:58  python3m -> python3.7m

As for the kernel script example, and its prerequisites header:

> Prerequisites:
>     Python version 2.7.x
>     gnuplot 5.0 or higher
>     gnuplot-py 1.8    

I'll change that to whatever is required moving forward and submit upstream.
It just has to be distro independent, obviously.

... Doug