[Python-Dev] handling the granularity of possible Py3K warnings in 2.6 (original) (raw)

Brett Cannon brett at python.org
Tue Jun 26 22:46:41 CEST 2007

My rewrite of import is written for 2.6. But I am going to try to bootstrap it into 3.0. But I want to bootstrap into 2.6 if it works out well in 3.0. That means coding in 2.6 but constantly forward-porting to 3.0. In other words I am going to be a guinea pig of our transition plan.

And being the guinea pig means I want to know where we want to take the Py3K warnings in 2.6. As of right now the -3 option causes some DeprecationWarnings to be raised (mostly about callable and dict.has_key). But I was thinking that a certain level of granularity existed amongst what should be warned against.

There is syntactic vs. semantic. For syntactic there is stuff you can do in versions of Python older than 2.6 (e.g., backtick removal), stuff you can only do in 2.6 (e.g., new exception syntax), or stuff that you can't do at all without a future statement (e.g., 'print').

For semantics, there is removal (e.g., callable), and then there is new semantics (dict.items).

What I was thinking was having these various types of changes be represented by proper warnings. That allows for using the -W option to control what warnings you care about.

So I envision something like:

future statement.

The key point is that when I am forward-porting I want to easily tell what syntax changes I can deal with now in older, e.g. 2.5 code, stuff that I can change directly in 2.6, and stuff that requires 2to3 or a future statement. Similar idea for semantic changes. That way I can do this all in steps.

Does this sound reasonable to people at all?

-Brett

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