Pythonic way to check if something exists?

Question

This is pretty basic but I was coding and started wondering if there was a pythonic way to check if something does not exist. Here\'s how I do it if its true:

Answer 1

What about the negation?

if not var:
    print 'nope it does not'

Though this is to see if the var is false / none and would blow up if var is not defined.

To see if var is defined:

try:
    var
except NameError:
    print 'not defined'