Re: [dpdk-dev] [PATCH 0/9] python2 deprecation notice

[Stephen Hemminger <stephen@networkplumber.org>]

On Fri, 17 Jul 2020 13:42:09 +0100
Bruce Richardson <bruce.richardson@intel.com> wrote:

> On Thu, Jul 16, 2020 at 02:01:21PM -0700, Stephen Hemminger wrote:
> > On Thu, 16 Jul 2020 16:44:29 +0200
> > Robin Jarry <robin.jarry@6wind.com> wrote:
> >   
> > > 2020-07-13, Bruce Richardson:  
> > > > In the absense of a "proper" solution, is the simplest option to
> > > > change the shebangs to all be python3, but leave the python2
> > > > compatibility in place, and add the warnings for anyone running it
> > > > explicitly using python2?     
> > > 
> > > I have found a hacky[1] but somewhat not too ugly way to dynamically use
> > > any available python interpreter.
> > > 
> > > Basically, the scripts shebangs become:
> > > 
> > >  #!/bin/sh
> > >  # shell script hack to dynamically use any available python interpreter
> > >  ''':'
> > >  if command -pv python3 >/dev/null 2>&1; then
> > >    exec python3 "$0" "$@"
> > >  else
> > >    exec python2 "$0" "$@"
> > >  fi
> > >  '''
> > >  # real python code starts here
> > > 
> > > This hack obviously would remain only for the time where we still have
> > > python 2 support and can be removed after 20.08 is released.
> > > 
> > > What do you think?
> > > 
> > > [1] https://unix.stackexchange.com/a/66242
> > >   
> > 
> > No.  
> 
> I could live with this, but I think that python3 is widespread enough now
> to just go with the simpler solution of python3 by default while still
> allowing others to run with python2 explicitly if they so desire.
> 
> I think we have covered a number of options, but I'm not sure we have
> converged on an agreed solution. Here are the options I would consider:
> 
> 0. Do nothing to the code, and just print deprecation notice in docs. This
>   will violate the previously documented plan, but won't break anything for
>   anyone.
> 1. Just add deprecation notice but leave shebang lines unchanged, meaning
>   lots of people see the notice but don't need to care since they just call
>   the script.
> 2. As #1, but check if python3 is available and only print deprecation
>   notice if not
> 3. Add deprecation notice, and change shebang lines to use python3. This
>   means that anyone who does not have python3 installed will see a breaking
>   change
> 4. Change shebangs to use python3 and detect at "make" build time if
>   python3 is available. If py3 is unavailable, adjust shebang and add
>   deprecation warning on "make install".
> 5. Use shell-hack above.
> 
> Any other options I'm missing?
> 
> For me, I think I can live with all options bar #1. Probably my top
> preference would be #4 or #2, with #0 and #4 next best thereafter.
> 

6. Change shebangs to use python3 and don't bother detecting.
   Since distributions will have python3.

7. Change shebangs and keep the python2 compat imports

8. Other alternative I have seen in code is to use
   try block in the import section:

try:
    # for Python2
    from Tkinter import *
except ImportError:
    # for Python3
    from tkinter import *

But supporting python2 for a longer time makes no sense.

I would go for #0 for 20.08 and full python3 in 20.11 (#3)