[Python-Dev] The Need for a Declarative Syntax Element (aka (original) (raw)

Jewett, Jim J jim.jewett at eds.com
Mon Apr 5 11:40:14 EDT 2004

Mike Pall:

It is unclear whether we have any use case that requires storing a different name ...

When adapting another module or library, it is often desirable to expose both the original name (for people familiar with the original) and a cleaned up name (so that your module can be used with internally consistent naming).

The current syntax is to bind a second name to the object after it is defined; that second binding could reasonably move into a decorator. Ensuring that it points to a final-enough version of the object is probably the programmer's responsibility.

Using declare

[See the original for more detail - basically, decorators must have a declare slot which will be called.]

I think this is the first non-arbitrary restriction we have seen on decorators. It does largely solve the old-code- might-run-differently issue, though not the old-interpreters- might-silently-run-code-undecorated issue.

Your suggested markers of [| |] or <| |> also solve that, as would a new keyword. A new word has the advantage of stating explicitly what it means, which allows additional extensions (some of which you already suggested).

Defining a decorator API also allows more freedom for the decorators; the declare API could accept more than just the target object. For example, it could take keywords giving the dictionary where the object will eventually be defined, or the name that will be used. (These would reduce the need for _getframe.)

-jJ

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