[Python-Dev] Documentation idea

[Brett Cannon]

On Fri, Oct 10, 2008 at 9:46 PM, Terry Reedy <tjreedy at udel.edu> wrote:
> Brett Cannon wrote:
>>
>> On Fri, Oct 10, 2008 at 1:45 PM, Terry Reedy <tjreedy at udel.edu> wrote:
>
>>> The advantage of the decorator version is that the compiler or module
>>> loader
>>> could be special cased to recognize the 'C' decorator and try it first
>>> *before* using the Python version, which would serve as a backup.  There
>>> could be a standard version in builtins that people could replace to
>>> implement non-standard loading on a particular system.  To cater to other
>>> implementations, the name could be something other than 'C', or we could
>>> define 'C' to be the initial of "Code" (in the implementation language).
>>>  Either way, other implementation could start with a do-nothing "C"
>>> decorator and run the file as is, then gradually replace with lower-level
>>> code.
>>>
>>
>> The decorator doesn't have to require any special casing at all
>> (changing the parameters to keep the code short)::
>>
>>  def C(module_name, want):
>>     def choose_version(ob):
>>         try:
>>           module = __import__(module_name, fromlist=[want])
>>           return getattr(module, want)
>>          except (ImportError, AttributeError):
>>            return ob
>>      return choose_version
>>
>> The cost is purely during importation of the module and does nothing
>> fancy at all and relies on stuff already available in all Python VMs.
>
> If I understand correctly, this decorator would only be applied *after* the
> useless Python level function object was created.

Yes.

>  I was proposing bypassing
> that step when not necessary, and I believe special casing *would* be
> required for that.

Yes, that would.

-Brett