[Python-Dev] Gradual migration
Tue, 24 Oct 2000 09:30:17 -0700
Guido van Rossum wrote:
> I think the proper approach is to start a separate migration process
> for each of these proposed changes.
As a more concrete extension to my last email, I propose the following
No major documented feature should be removed or have changed semantics
in Python 3000 or any other new version of Python until users have had a
year (preferably MORE!) of upgrade time. Upgrade time entails the
1. the released Python version has a new recommended way to
accomplish the task in a manner that will remain available in the
"breakage version" e.g. a div() function that people can use for a few
years while the semantics of "/" are in transition.
2. the mechanism/syntax that will be removed is formally deprecated.
The documentation would say, e.g. "You should not use '/' for now. It is
changing semantics in the future."
3. the released Python version sports a runtime warning to tell
users that the mechanism/syntax is going away. "CompatibilityError:
Future versions of Python will have different semantics for the '/'
operator. Please use div() instead."
The actual "right" amount of upgrade time depends on the extent of the
breakage and its ease of detection.
I can PEP this if people agree. I think that the user community would
appreciate our effort to promise not to break code suddenly and
Paul Prescod - Not encumbered by corporate consensus
Simplicity does not precede complexity, but follows it.