[Python-Dev] PEP 362 Third Revision (original) (raw)

Alexandre Zani alexandre.zani at gmail.com
Thu Jun 14 20:36:03 CEST 2012

On Thu, Jun 14, 2012 at 10:10 AM, Brett Cannon <brett at python.org> wrote:

On Thu, Jun 14, 2012 at 12:39 PM, Yury Selivanov <yselivanov.ml at gmail.com> wrote:

On 2012-06-14, at 12:32 PM, Benjamin Peterson wrote: > 2012/6/14 Yury Selivanov <yselivanov.ml at gmail.com>: >> On 2012-06-14, at 11:24 AM, Brett Cannon wrote: >>> On Thu, Jun 14, 2012 at 9:50 AM, Yury Selivanov >>> <yselivanov.ml at gmail.com> wrote: >>> >>> [SNIP] >>> >>> Let's consider replacement of 'Parameter.is*' set of attributes with >>> a single 'Parameter.kind' attribute, which will have the following >>> possible values: 'positional', 'vararg', 'keyword-only', 'varkwarg'. >>> >>> (I think 'positional' is more intuitive than 'index'?) >>> >>> >>> +1 if this change is made. >> >> How about adding 'kind' and keeping 'is*' attributes, >> but making them read-only dynamic properties, i.e.: >> >>   class Parameter: >>       ... >> >>       @property >>       def isvararg(self): >>           return self.kind == 'vararg' >> >>       ... >> >> ? > > Seems a bit bloatly to me. (One way to do it.) Yes, but on the other hand it solves "strings are error prone" argument, keeps all 'is*' attributes in sync, and makes them read-only. 'kind' property may do validation on set, to diminish mistakes probability even further. I agree with Benjamin, it goes against TOOWTDI without enough of a justification to break the rule. Just make the strings constants on the Parameter class and you solve the lack of enum issue.

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I don't think it really breaks TOOWTDI because you're talking about two use-cases. In one case, you're checking if something is a particular kind of parameter. In the other case, you're doing some sort of dict-based dispatch. I also think is_args etc is cleaner to use when doing a comparison:

if param.is_arg:

vs

if param.kind == param.ARG:

That said, it's not a huge deal and so I won't push this any more than I already have.

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