[Python-ideas] from __past__ import division, str, etc

[Steven D'Aprano]

On Wed, Jan 08, 2014 at 05:22:02PM +0100, Alejandro López Correa wrote:
[...]
> Anyway, I understand it is not a clean way to proceed, but something along
> these lines might be the only way to speed up the adoption of python 3

One assumption in this discussion, and the various related discussions 
on Reddit and other places, is that adoption of Python 3 is too slow and 
needs to be sped up. I don't believe this is true. I believe adoption 
is just right and exactly what should be expected.

Alex Gaynor wrote a blog post a week or so ago claiming that, five years 
since Python 3 was first released, everyone should have migrated by now 
and that since only "five percent" (a figure which I believe he pulled 
out of thin air) have migrated, Python 3 has been a failure.

I challenge that belief. I've been hanging around here and on the 
Python-Dev list for a long time, and while I can't find any official 
pronouncement, the sense has always been that Python 3 adoption will 
take ten years, not five. (That's my recollection -- if any of the core 
developers wish to correct me, please do.) Rates of adoption are much, 
much higher than gossip on the Internet suggests. About 70% of the top 
200 projects on PyPI support Python 3, and downloads of Python 3 are 
very healthy, possibly even higher than downloads of Python 2. On the 
tutor list, I see a significant number of beginners using Python 3.

It seems to me that given the circumstances, Python 3 adoption is right 
where we should expect it to be half-way through a decade-long process. 
There will be a period at the start when hardly anyone will migrate, 
then a period of accelerating migration, which will accelerate further 
when the mainstream Linux distros start shipping Python 3 as their 
system Python (ArchLinux is not mainstream, but Fedora is planning the 
change), followed by a sudden rush in another four or five years when 
people realise that Python 2.7 becoming unmaintained is no longer a 
distant prospect but is about to happen.

For many people, waiting until the last minute is the most sensible 
thing that they can do. This gives time for the early adoptors to 
discover and iron out all the wrinkles and difficulties. Rather than 
approaching this as "Python 3 has been a failure, what can we do to save 
it?" we should be approaching this as "Python 3 has been a success, what 
lessons can we take from the early adoptors to make it even easier for 
the next wave of adoptors?"

"from __past__ import spam" does not make it easier to adopt. It just 
makes it easier to *put off adopting*.


> and minimise the risk of defection to other languages.

People threaten that, but it is an irrational threat. (Mind you, people 
do silly, irrational things every day.) If you think its hard to migrate 
from Python 2 to 3, when you get to keep 90% of your code base and most 
of the backward-incompatible changes are a few libraries that have been 
renamed and a handful of syntax changes, how hard will it be to throw 
away 100% of your code and start again with a completely different 
language?



-- 
Steven