Menu
I have some questions about user-defined exceptions in Python and how they should be organized in a complete project.
I have a fairly complex python project with some sub-packages that has the following structure (__init__.py omitted):
/docs (Documentation)
/apidocs (generated API documentation)
/askindex (my application package)
/test (Unit tests directory)
test_utils.py
... (more tests)
/workers (various worker classes)
communicators.py
processes.py
threads.py
utils.py
main.py (contains the starting point)
data_objects.py (various objects used all around the application)
settings.py (settings of the application)
README.txt
I would like to implement my own Exception to use them in the modules of the 'workers' package for specific errors.
Where should I place these exceptions ? I know that I should have my own base exception which subclasses the standard Exception class and subclass it for my other exceptions. Should I create a new 'exceptions' module under 'workers' ? Put exception classes in the module in which they're raised ? In this case, where should I put my base class ? Is my application structure appropriated ?
I am new to exceptions in Python, so please excuse me if the answer is obvious...
679
Python Language Exceptions Exception Hierarchy Exception handling occurs based on an exception hierarchy, determined by the inheritance structure of the exception classes. For example, IOError and OSError are both subclasses of EnvironmentError . Code that catches an IOError will not catch an OSError .
The hierarchy of Exceptions in the Java programming language begins with the Throwable class – which comes from the Object class and is its direct subclasswhileThe Exception class presents all This Throwable class further branches into two subclasses – Error and Exception.
In Python, users can define custom exceptions by creating a new class. This exception class has to be derived, either directly or indirectly, from the built-in Exception class. Most of the built-in exceptions are also derived from this class.
User Defined Exception or custom exception is creating your own exception class and throws that exception using 'throw' keyword. This can be done by extending the class Exception. There is no need to override any of the above methods available in the Exception class, in your derived class.
In general I've found with my own work that when I want a custom type of exception, it's specific to a particular module or package. If it's relevant to a module, I put it just in that module. I haven't yet found a case where it would be neater to have a module or package dedicated to exceptions.
Examples: if I have a jester module, with a class Juggler in it with a method juggle which can raise a DroppedBall (cue throwing rotten tomatoes or similar), the DroppedBall would be in the jester module. Then the crowd.Person instances could try watching the juggler and except jester.DroppedBall.
If I had a package food, with various modules in it, fruit, vegetable, etc. which all have an eat method (inherited from food.Foodstuff, doubtless), they might be able to raise a RottenException, which would naturally belong in the root of the food package: __init__.py.
142
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With
