[Types-sig] IsInstance

[Paul Prescod]

Guido van Rossum wrote:
> Perhaps this could be an extension of isinstance()?  (That already
> takes both class and type objects.)

I wanted the function to return an object:

myList=isinstance( foo, types.ListType )
if not myList:
	myDict=isinstance( foo, types.DictionaryType )

Then we can do the inferencing by looking at a single statement. Compare
it to this:

if isinstance( foo, types.ListType ):
	myList=foo
elif isinstance( foo, types.DictionaryType ):
	myDict=foo

That inferencing is just too hard. It isn't a proper cast operator
anymore. If you are willing to change isinstance to return the object if
it matches then I would like to use it.

-- 
 Paul Prescod  - ISOGEN Consulting Engineer speaking for himself
Three things to be wary of: A new kid in his prime
A man who knows the answers, and code that runs first time
http://www.geezjan.org/humor/computers/threes.html