if hasattr(a, 'property'): a.property
EDIT: See zweiterlinde's answer below, who offers good advice about asking forgiveness! A very pythonic approach!
The general practice in python is that, if the property is likely to be there most of the time, simply call it and either let the exception propagate, or trap it with a try/except block. This will likely be faster than
hasattr. If the property is likely to not be there most of the time, or you're not sure, using
hasattr will probably be faster than repeatedly falling into an exception block.