Try hasattr():
if hasattr(a, 'property'):
a.property
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.
Maybe I missed the question, but why not:
class MyException(Exception):
pass
To override something (or pass extra args), do this:
class ValidationError(Exception):
def __init__(self, message, errors):
# Call the base class constructor with the parameters it needs
super().__init__(message)
# Now for your custom code...
self.errors = errors
That way you could pass dict of error messages to the second param, and get to it later with e.errors.
In Python 2, you have to use this slightly more complex form of super():
super(ValidationError, self).__init__(message)
Best Answer
Some of my workmates are working on Ironclad, a project that will make extension modules for CPython work in IronPython. It's still in development, but parts of numpy, scipy and some other modules already work. You should try it out to see whether the parts of scipy you need are supported.
It's an open-source project, so if you're interested you could even help. In any case, some feedback about what you're trying to do and what parts we should look at next is helpful too.