Check undefined variable

[Chris Gonnerman]

On Tue, 30 Jul 2002 09:24:57 -0600, Daniel Fackrell wrote:
> "Michael Grabietz" <michael.grabietz at img-online.de> wrote in message
> news:3D46AD2E.709 at img-online.de...
> > how is it possible to check whether a variable 'a' is undefined or not.
> >
> > e.g.:
> >
> > if a==NULL :                 # something like that
> >      print 'a is undefined !'
> >      else
> >      print 'a already undefined !'
> 
> try:
>     type(A)
>     print 'A exists'
> except NameError:
>     print 'A doesn't exist'

Actually this works:

	try:
		A
		print "A exists"
	except NameError:
		print "A doesn't exist"

in other words, just call out the name and see if it answers :-)