Exception Handling in Python

Custom Exceptions

Code similar to that seen above can be used to create custom exceptions and pass information along with them. This can be extremely useful when trying to debug complicated projects. Here is how that code would look; first creating the custom exception class:

  class CustomException(Exception):
      def __init__(self, value):
          self.parameter = value
      def __str__(self):
          return repr(self.parameter)

And then using that exception:

try:
    raise CustomException("My Useful Error Message")
except CustomException, (instance):
    print "Caught: " + instance.parameter