How to determine if a variable exists in another Python file

Question

I have two python files. From python file #1, I want to check to see if there is a certain global variable defined in python file #2.

What is the best way to do this?

Answer 1

try:
    from file import varName
except ImportError:
    print 'var not found'

Alternatively you could do this (if you already imported the file):

import file
# ...
try:
    v = file.varName
except AttributeError:
    print 'var not found'

This will work only if the var is global. If you are after scoped variables, you'll need to use introspection.

Answer 2

You can directly test whether the file2 module (which is a module object) has an attribute with the right name:

import file2
if hasattr(file2, 'varName'):
    # varName is defined in file2…

This may be more direct and legible than the try… except… approach (depending on how you want to use it).