Check existence of members/methods

From: Nicolas Fleury (nid_oizo_at_yahoo.com_remove_the_)
Date: 09/03/04 

Date: Thu, 02 Sep 2004 18:30:46 -0400

Hi everyone,
        I'm wondering what is the easiest/cleanest way to look for existence of
available methods/members.

For example, in parsing a xml file, created objects can define a
setXmlFilename function or a xmlFilename member to get the filename they
are from.

Right now I have the following code:

try: object.setXmlFilename
except:
     try: object.xmlFilename
     except: pass
     else: object.xmlFilename = currentFilename
else: object.setXmlFilename(currentFilename)

But it looks a bit wierd, since it's like a "if" with the false
consequence presented first. I wonder if there is, and if there should
be a better way to do it. I could also do the following:

def noraise(expressionString):
     try: eval(expressionString)
     except: return True
     return False

if noraise("object.setXmlFilename"):
     object.setXmlFilename(currentFilename)
elif noraise("object.xmlFilename"):
     object.xmlFilename = currentFilename

But it puts code in strings, which I feel less natural. What do you
think about it? Have I miss a better solution or is there something for
that in the language?

Regards,
Nicolas