Robert Bradshaw, 13.03.2010 21:07:
> On Mar 13, 2010, at 5:30 AM, Stefan Behnel wrote:
>> a) compatibility with Py2 code (->  when compiling .py files)
>> b) compatibility with Py3 code (->  .py files + "-3" option or
>> "cython3")
>> c) the Cython language (->  .pyx files)
>>
>> We don't currently care about the file extension, for example.
>> Should we generally stop supporting the 'cdef' keyword in .py files?
>
> The only place that the extension currently matters is that with a .py
> file, signatures and other declarations don't have to match what they
> are in the .pxd file (the ones from the .pxd file get pulled over).
> This may result in compile time errors, when renaming a .py file to
> a .pyx file, which I'm OK with, but we should definitely avoid any
> behavioral changes due to changing the file extension.

The only reason why a user would choose the .py extension is because the 
code should work also in plain CPython, i.e. purely pure mode. So, what I 
meant was: when compiling a .py file, we should keep Cython specific syntax 
(especially keywords) out of the way, so that Cython can compile as much 
Python code as possible. I agree that it shouldn't result in any semantic 
differences for Python constructs.


> The -3 option would be completely orthogonal to the file extension,
> and could be used with both .py and .pyx files.

Makes sense.


>> I think we need to do that if we really want to introduce a well
>> defined notion of "language level compatibility".
>
> What I want is that Cython is a superset of Python. In particular, for
> widespread use it should be safe (barring bugs) to just compile a .py
> file and run it. I don't think our "language level compatibility"
> needs to be more granular than Py2 (meaning specifically 2.6, or maybe
> 2.7) and Py3 (meaning 3.1?), at least not right now (there are bigger
> fish to fry).

Ok, let's assume that most Py3 syntax that we support will make it into 
Py2.7 anyway, so targeting something close to 2.7 should work.

Stefan
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