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:

var = 1 if var:     print 'it exists' 

but when I check if something does not exist, I often do something like this:

var = 2 if var:     print 'it exists' else:     print 'nope it does not' 

Seems like a waste if all I care about is knIs there a way to check if something does not exist without the else?

Answer 1

LBYL style, "look before you leap":

var_exists = 'var' in locals() or 'var' in globals() 

EAFP style, "easier to ask forgiveness than permission":

try:     var except NameError:     var_exists = False else:     var_exists = True 

Prefer the second style (EAFP) when coding in Python, because it is generally more reliable.