[Python-Dev] sys.implementation

Wed May 9 03:14:02 CEST 2012

Hi Eric,
Great job on the latest PEP 421. I really like it. A few additional
comments/questions.
 * sys.implementation.version
 This is defined as the version of the implementation, while
 sys.version_info is the version of the language. The semantics of
 sys.version_info have been sufficiently squishy in the past, as the XXX
 implies. This PEP shouldn't try to untangle that, so I think it be better
 to represent both values explicitly in sys.implementation.
 * Adding new required variables. I'd claim that it's not unduly heavyweight
 to require a new PEP to add required variables to sys.implementation. That
 hypothetical PEP will have to include things like rationale, impact on
 other implementations, etc. That seems like enough to warrant a new PEP,
 even if it's relatively succinct.
 I'd also make it clear that adding new variables to
 sys.implementation.metadata explicitly does *not* require a PEP.
 * In Example Metadata Value:
 "If they later have meaningful uses cases, they can be added by following
 the process described in Adding New Required Attributes."
 I'd rephrase this to "If these or any other variables are deemed to have
 meaningful use cases across all implementations, they can be moved or added
 to sys.implementation directly, following the process described in Adding
 New Required Attributes."
 * I mildly prefer sys.implementation.name to be lower cased. My intuition is
 that to be safe, most comparisons of the value will coerce to lower case,
 which is easy enough in Python, but perhaps a bit more of a pain in C. I
 don't feel really strongly about this though. (A counter argument is that
 the value might be printed, so a case-sensitive version would be better.)
 * Since I'm advocating to be explicit about the language version and the
 implementation version, .hexversion is probably also useful for both.
 * I've said before that I think the keys in sys.implementation should be
 locked down (i.e. not writable). I think sys.implementation.metadata
 should be the same type.
Cheers,
-Barry
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