How do I check if a variable exists?

I want to check if a variable exists. Now I'm doing something like this:

try:
    myVar
except NameError:
    # Do something.

Are there other ways without exceptions?

To check the existence of a local variable:

if 'myVar' in locals():
  # myVar exists.

To check the existence of a global variable:

if 'myVar' in globals():
  # myVar exists.

To check if an object has an attribute:

if hasattr(obj, 'attr_name'):
  # obj.attr_name exists.

Stack Overflow Q#843277, score: 2373