Exception example in Python

pyexn.py

class MyExn(Exception):
    def __init__(self, value):
        self.value = value
    def __str__(self):
        return "MyExn raised with value " + str(self.value)

def example():
    try:
        raise MyExn(0)
    except MyExn, e:
        print e

if __name__ == '__main__':
    example()
    # results in: "MyExn raised with value 0"