[Python-Dev] Re: @deprecated

Michael Chermside mcherm at mcherm.com
Wed Mar 9 15:08:06 CET 2005

[I followed Greg's suggestion and proposed a "deprecated" decorator.]

Raymond writes:
> Decorators like this should preserve information about the underlying
> function

Of course! The version I posted was intended to illustrate the idea, not
to be a clean implementation. A long time ago, I proposed a
decorator-maker-decorator (see "Creating Well-Behaved Decorators"
in http://www.python.org/moin/PythonDecoratorLibrary), and I still think
it's probably a wise approach since it's easy for people to be careless
and forget to preserve these sorts of features.

Jim Jewett writes:
> I agree that it should go in the cookbook, but I think you should
> set the category to a DeprecationWarning and give the offending
> function's name.

I had wondered about that, but wasn't familiar with how people actually
use categories. DeprecationWarning certainly sounds right, or is there
some reason why I should use a custom subclass of DeprecationWarning?

Michael Hudson and Irmen point out:
> One difference: I imagine (hope!) the java compiler would complain if
> the deprecated function is referenced, whereas the python version only
> complains if it is called...

True enough. And java doesn't complain at all if the deprecated function
is invoked via reflection. It's a fundamental difference in style between
the two languages: Python barely even HAS a "compile phase", and Python
programs tend to be far more dynamic than Java.

-- Michael Chermside

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