[tlug] Python 2 versus Python 3 (was: Re: Distro support matrix)

["Stephen J. Turnbull" <stephen@example.com>]

jep200404@example.com writes:

 > So if you want to write a big program in Python, 
 > you probably start with the newest version of Python 2, 

Not really.  If you want to add features to a big program written in
Python 2, you probably start with the newest version of Python 2.  But
if you're going to write a new big program, you need to do an overall
design, then look at the libraries available for Python 2 and Python
3 to see which offers the best combination of ease of implementation
and future-proofing.

For example, if you're focused on scientific calculation, almost all
of SciPy and NumPy are working well under Python 3.  If you're doing
high-performance webapps, the decision is harder, but the balance is
rapidly tipping toward Python 3 there, too (Twisted is now usable for
many products, and Guido's own pet project right now is a
lighter-weight asynchronous framework called Tulip.)

 > which seems to be 2.7.5 from 2013-05-15. 
 > The newest (stable?) version of Python 3 seems to be 3.3.2 
 > from 2013-05-15.

That's right.  Python 3.4 is in alpha now.

 > Both Python 2 and Python 3 are actively maintained. 

For values of "actively maintained" that are different for version 2
and version 3.  For practical purposes, Python 2 is now in bugfix-only
mode (it's sometimes possible to sneak in minor features along with
bugfixes if the feature used to cause an undocumented error, but
that's about the limit).  For example, Enums were recently added to
the stdlib in Python 3 and a simple statistics packages is just about
to be added, but Python 2 will never get them.  (In practice this only
matters if you have a very strict corporate policy about "approved
software", as it's very easy to install Python-2.7-compatible versions
of these packages from the Cheeseshop.)