Re: [RFC/PATCH] CodingGuidelines: add Python code guidelines
On Fri, Jan 18, 2013 at 11:04:15AM -0800, Junio C Hamano wrote: John Keeping j...@keeping.me.uk writes: diff --git a/Documentation/CodingGuidelines b/Documentation/CodingGuidelines index 69f7e9b..baf3b41 100644 --- a/Documentation/CodingGuidelines +++ b/Documentation/CodingGuidelines @@ -179,6 +179,22 @@ For C programs: - Use Git's gettext wrappers to make the user interface translatable. See Marking strings for translation in po/README. +For Python scripts: + + - We follow PEP-8 (http://www.python.org/dev/peps/pep-0008/). + + - As a minimum, we aim to be compatible with Python 2.6 and 2.7. + + - Where required libraries do not restrict us to Python 2, we try to + also be compatible with Python 3. In this case we use + `from __future__ import unicode_literals` if we need to differentiate + Unicode string literals, rather than prefixing Unicode strings with + 'u' since the latter is not supported in Python versions 3.0 - 3.2. In this case? In what case? This document will stay effective long after you settle one particular backward incompatibility Python 3 introduced, namely, the unicode literal issues. It is just one example. I meant in the case where you are supporting Python 3 but I suspect it would be better to move the unicode_literals sentence to a new bullet. Or maybe we should just remove it - I haven't seen a case in the current Git source where we need Unicode literals. That example somehow tells me that early versions of Python 3.x series may be too buggy and not worth worrying about, and we may want to set a floor for Python 3.x series, too, with something like: [snip] I am not actively advocating to disqualify early 3.x; I am just suggesting that doing so may be a viable escape hatch for us that does not harm real users. If you and others who know Python better think there isn't any problem that makes it too cumbersome to support both late 2.x and 3.0/3.1, there is no reason to set the floor at 3.2. I just have this feeling that we might be better off treating them as 0.x releases of a new software called Python3, that happens to be similar to the Python we know. I originally thought about putting a floor of 3.3 (which is where Unicode literals were reintroduced) but that was only released in September and as far as I'm aware Unicode literals are the only reason to have a restriction on Python 3 versions, given that we support Python 2.6 - standard library features should be equivalent. I don't think Python 3.0 is any less stable than any other 3.x release, it's just that it was the first release which attempted a clean break from backwards compatibility. From the point of view of features supported, Python 2.6 and 3.0 should be roughly equivalent - they were released together with the intent that 2.6 should make it possible to write code that ports to 3.0 easily, using 2to3. As more people have started trying to support Python 3 in the wild, it has become clear that it is often easier to have a single codebase that works with both Python 2 and Python 3, and not use 2to3. It is for this reason that the Unicode literal prefix was reintroduced. From the specification reintroducing it [1]: Complaint: Python 3 shouldn't be made worse just to support porting from Python 2 This is indeed one of the key design principles of Python 3. However, one of the key design principles of Python as a whole is that practicality beats purity. [1] http://www.python.org/dev/peps/pep-0414/#complaint-python-3-shouldn-t-be-made-worse-just-to-support-porting-from-python-2 John -- To unsubscribe from this list: send the line unsubscribe git in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [RFC/PATCH] CodingGuidelines: add Python code guidelines
On Fri, Jan 18, 2013 at 12:25:34PM -0800, Junio C Hamano wrote: John Keeping j...@keeping.me.uk writes: As more people have started trying to support Python 3 in the wild, it has become clear that it is often easier to have a single codebase that works with both Python 2 and Python 3, and not use 2to3. It is for this reason that the Unicode literal prefix was reintroduced. Yes, and from that perspective, placing floor on earlier 3.x makes tons of sense, no? These early versions may not be unstable in the this does not behave as specified in the language specification for 3.x sense, but for the purpose of running scripts meant to be executable by both 2.x and 3.x series, the early 3.x versions are not as good as later versions where Python folks started making deliberate effort to support them. As far as I'm aware (and having reviewed the release notes for 3.1, 3.2 and 3.3 as well as the planned features for 3.4), Unicode literals are the only feature to have been added that was intended to make it easier to support Python 2 and 3 in the same codebase. Given that no code currently on pu uses Unicode literals, I don't see a reason to specify a minimum version of Python 3 since we're already restricting ourselves to features in 2.6. John -- To unsubscribe from this list: send the line unsubscribe git in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [RFC/PATCH] CodingGuidelines: add Python code guidelines
John Keeping j...@keeping.me.uk writes: On Fri, Jan 18, 2013 at 12:25:34PM -0800, Junio C Hamano wrote: John Keeping j...@keeping.me.uk writes: As more people have started trying to support Python 3 in the wild, it has become clear that it is often easier to have a single codebase that works with both Python 2 and Python 3, and not use 2to3. It is for this reason that the Unicode literal prefix was reintroduced. Yes, and from that perspective, placing floor on earlier 3.x makes tons of sense, no? These early versions may not be unstable in the this does not behave as specified in the language specification for 3.x sense, but for the purpose of running scripts meant to be executable by both 2.x and 3.x series, the early 3.x versions are not as good as later versions where Python folks started making deliberate effort to support them. As far as I'm aware (and having reviewed the release notes for 3.1, 3.2 and 3.3 as well as the planned features for 3.4), Unicode literals are the only feature to have been added that was intended to make it easier to support Python 2 and 3 in the same codebase. So there may be some other incompatibility lurking that we may run into later? Given that no code currently on pu uses Unicode literals, I don't see a reason to specify a minimum version of Python 3 since we're already restricting ourselves to features in 2.6. OK, at least that reasoning need to be kept somewhere, either in the documentation of in the log message. Thanks. -- To unsubscribe from this list: send the line unsubscribe git in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [RFC/PATCH] CodingGuidelines: add Python code guidelines
On Fri, Jan 18, 2013 at 02:26:06PM -0800, Junio C Hamano wrote: John Keeping j...@keeping.me.uk writes: On Fri, Jan 18, 2013 at 12:25:34PM -0800, Junio C Hamano wrote: These early versions may not be unstable in the this does not behave as specified in the language specification for 3.x sense, but for the purpose of running scripts meant to be executable by both 2.x and 3.x series, the early 3.x versions are not as good as later versions where Python folks started making deliberate effort to support them. As far as I'm aware (and having reviewed the release notes for 3.1, 3.2 and 3.3 as well as the planned features for 3.4), Unicode literals are the only feature to have been added that was intended to make it easier to support Python 2 and 3 in the same codebase. So there may be some other incompatibility lurking that we may run into later? I doubt it - enough projects are running on Python 2 and 3 now that I doubt there's anything unexpected left to hit. Given that no code currently on pu uses Unicode literals, I don't see a reason to specify a minimum version of Python 3 since we're already restricting ourselves to features in 2.6. OK, at least that reasoning need to be kept somewhere, either in the documentation of in the log message. I'll put it in the log message when I send this as a proper patch. John -- To unsubscribe from this list: send the line unsubscribe git in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
