[Python-Dev] Backwards Incompatibility

[Jeremy Hylton]

>>>>> "PP" == Paul Prescod <paulp@ActiveState.com> writes:

  PP> Jeremy Hylton wrote:
  >>
  >> I don't recall seeing any substanital discussion of this PEP on
  >> python-dev or python-list, nor do I recall a BDFL decision on the
  >> PEP.  There has been lots of discussion about backwards
  >> compatibility, but not much consensus.

  PP> We can have the discussion now, then. In my opinion it is
  PP> irresponsible to knowingly unleash backwards incompatibilities
  PP> on the world with no warning. If people think Python is unstable
  PP> it will negatively impact its growth much more than the delay of
  PP> some esoteric features. 

You have a colorful way of writing :-).  When we unleashed Python
2.1a1, there was a fair amount of discussion about nested scopes on
python-dev and on python-list.  The fact that code would break has
been documented in the PEP since December, before the BDFL pronounced
on it. 

Why didn't you say it was irresponsible then? <0.5 wink>  If you're
just repeating your earlier arguments, I apologize for the rhetoric
:-). 

  PP> Let me put the ball back in your court:

  PP> Is the benefit provided by having nested scopes this year rather
  PP> than next year worth the pain of howls of outrage in
  PP> Python-land. If we give people a year to upgrade (with warning
  PP> messages) they will (rightly) grumble but not scream.

I've heard plenty of hypothetical howls and one real one, from Mark.
The alpha testing hasn't resulted in a lot of other complaints.  I
just asked on c.l.py for problem reports and /F followed up with a
script to help find problems.  Let's see what the result is.

I ran Fredrik's script over 4700 source files on my machine and found
exactly four errors.  Two were from old copies of the Python CVS tree;
they've been fixed in the current tree.  One was from Zope and another
was an *old* jpython test case.

Jeremy