[IPython-dev] [sympy] Treating Python 3 as a first-class citizen

Aaron Meurer asmeurer at gmail.com
Mon Aug 5 23:24:37 EDT 2013

On Mon, Aug 5, 2013 at 1:40 PM, Thomas Kluyver <takowl at gmail.com> wrote:
> On 5 August 2013 19:32, Ondřej Čertík <ondrej.certik at gmail.com> wrote:
>> Though the PEP above says that eventually "python" should point to python
>> 3.
> Debian developers are strongly against ever making that change. It's
> possible that they'll change their minds in a few years, but I wouldn't bank
> on it.

They will change their minds. I thought that Arch was stupid making
"python" point to Python 3, but that was because at the time, no
libraries were Python 3 compatible. Nowadays, all major libraries are
compatible. In the future, Python 2 will be defunct, and it will be
stupid to never call Python "python".

>> What is confusing to me is what is fundamentally different in Python 3.2,
>> as opposed to Python 2.5 or 2.6, when you have a single code base.
>> E.g. we do not bother with creating ipython2.5 and ipython2.6, so that
>> they
>> can be run side by side, and people simply use virtualenv to run them
>> side by side.
>> So why cannot the same approach be used for Python 3.2?
> Many more systems have a 2.x and a 3.x installed together, and many more
> users will want to run a 2.x and a 3.x version in parallel than wanted to
> run, say, 2.5 once 2.6 was available. I think the Debian approach of
> treating Python 2 and 3 as two separate, albeit similar, platforms works
> nicely.
> (In fact I think IPython used to make versioned entry points like
> ipython2.6, but that's not important).
> Thomas

Once you switch to a single codebase, you start to see things
differently. Python 3 is just another version of Python. Supporting
Python 2.6 - 3.3 is no different than supporting Python 2.4 - 2.7.

The Python community made a big fuss about it, but I think that was a
mistake, and it has kept people from transitioning.

Aaron Meurer

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