[Python-Dev] Common subset of python 2 and python 3 (original) (raw)
Markus Unterwaditzer markus at unterwaditzer.net
Thu Jan 16 13:52:18 CET 2014
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On Wed, Jan 15, 2014 at 01:22:44PM +0100, "Martin v. Löwis" wrote:
Am 12.01.14 18:39, schrieb Nachshon David Armon: >>> I propose that this new version of python use the python 3 unicode model. >>> As the version of python will be fully compatible with both python 2 and >>> with python 3 but NOT necsesarily with all existing code in either. It is >>> designed as a porting tool only.
I don't think that it is possible to write an interpreter that is fully compatible for all it accepts. Would you think that the program print(repr(2**80).endswith("L")) is in the subset that should be supported by both Python 2 and Python 3?
IMO Python 2 and 3 do have this part in common when you talk about valid syntax and available methods and functions, but not in terms of behavior. I think a new proposed Python version should simply crash on your example.
I'm kind-of playing devil's advocate here because i agree with previous posters that such a Python version is unneccessary with tox and "python2 -3"
Notice that it prints "True" in Python 2 and "False" in Python 3. So if this common-version interpreter rejects the above program, which operation (**, repr, endswith) would you want to ban from subset?
Warnings about using certain string methods on repr() might be a neat thing to add to "python -3" or static analysis tools.
Regards, Martin
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