Anybody still using Python2?

[Fred Wright]

On Wed, 29 Jan 2025, Hal Murray wrote:

>> It's not about "with" in the sense of what's on the system; it's about
>> what Python version *their code* works with.  Due to the large
>> incompatibilities between Python 2 and Python 3, it takes serious work to
>> update existing Python 2 code to work with Python 3.  And such fixes
>> often impact code paths which are rarely used and poorly tested, leading
>> to long-lurking bugs associated with such updates.  For example, SCons
>> was still fixing bugs related to Python 3 long after it dropped support
>> for Python 2 (making the "just run it with Python 2" workaround
>> impossible).
>
> That makes sense.  But I'm missing the next step.  Do sites still using
> mostly Python 2 have Python 3 available?  Are they writing new code in
> Python 2 or 3?

It's not about new code; it's about existing code that may not work with 
Python 3.

Also note that Python 3 isn't the only Python version that breaks stuff; 
it's just the most significant.  E.g., if you want a sane interaction 
between signals and select()/poll(), then you shouldn't use a version 
later than 3.4, since they intentionally broke it in 3.5.

> Can we build *with* 3 for *2* on those sites?  Or would we even need to?
> If they have 3 available, is it good enough if our code says it wants to
> run on "python3" rather than "python"?
>
> Does our code work in the build *with* 3 for *2* mode?  I expect if it
> finds 3 so it is building on 3 that it will build for 3 without a
> configure option that doesn't yet exist.
>
> We have:
>      --python=PYTHON     python binary to be used [Default:
> /usr/bin/python]
> But that doesn't say if it's *with* or *for* so I assume the split doesn't
> yet exist.

That option is for "for".  The "with" is defined by whatever Python 
version is used to run waf.  The option is intended to allow them to be 
different, but IIRC it doesn't currently work correctly, at least in some 
cases.

>> Is there some specific reason to want to move to a newer waf, or is it
>> just a case of wanting the latest shiny new thing?  Given the
>> excruciatingly poor state of waf documentation, the "if it ain't broke
>> don't fix it" philosophy is generally a safer choice.
>
> Not quite the shiny thing, but close.  There is:
>  ntpsec doesn't build with waf >= 2.1.0
>  https://gitlab.com/NTPsec/ntpsec/-/issues/830
> but that's based on:
>  If not using the waf script bundled with ntpsec (as might be
>  required by distro-specific packaging guidelines),

Ah, I wasn't aware that it ever used an unbundled waf.

> It would be nice to get the python 2 tangle out of the way.  In one sense,
> it's not a big deal.  On the other hand, it's several minor pains in the
> ass.
>
> How many people/distros are running python 2 without python 3 being
> available and also want to run ntpsec?

It's not about whether Python 3 is available, but about whether it's 
usable for whatever code they may have that uses ntpsec's Python modules.

On Thu, 30 Jan 2025, Hal Murray via devel wrote:

>
> Richard Laager said:
>> Are there platforms (still worth supporting) that have Python 2 but not
>> Python 3 out of the box?
>
> I think that's the key question.

Actually, no.  That only applies to the "with", not the "for".

Anyone needing Python 2 can install it from a package, so it's not just 
about what's bundled with the distro.  Note that ntpsec itself is often 
not bundled with a given distro, which doesn't mean that it can't be used 
if someone wants it.

Fred Wright