error-handling

Error Handling

Implement various kinds of error handling and resource management.

An important point of programming is how to handle errors and close resources even if errors occur.

This exercise requires you to handle various errors. Because error handling is rather programming language specific you'll have to refer to the tests for your track to see what's exactly required.

Hints

For the filelike_objects_are_closed_on_exception function, the filelike_object will be an instance of a custom FileLike class defined in the test suite. This class implements the following methods:

• open and close, for explicit opening and closing.
• __enter__ and __exit__, for implicit opening and closing.
• do_something, which may or may not throw an Exception.

Exception messages

Sometimes it is necessary to raise an exception. When you do this, you should include a meaningful error message to indicate what the source of the error is. This makes your code more readable and helps significantly with debugging. Not every exercise will require you to raise an exception, but for those that do, the tests will only pass if you include a message.

To raise a message with an exception, just write it as an argument to the exception type. For example, instead of raise Exception, you should write:

raise Exception("Meaningful message indicating the source of the error")

Running the tests

To run the tests, run the appropriate command below (why they are different):

• Python 2.7: py.test error_handling_test.py
• Python 3.4+: pytest error_handling_test.py

Alternatively, you can tell Python to run the pytest module (allowing the same command to be used regardless of Python version): python -m pytest error_handling_test.py

Common pytest options

• -v : enable verbose output
• -x : stop running tests on first failure
• --ff : run failures from previous test before running other test cases

For other options, see python -m pytest -h

Submitting Exercises

Note that, when trying to submit an exercise, make sure the solution is in the $EXERCISM_WORKSPACE/python/error-handling directory.

You can find your Exercism workspace by running exercism debug and looking for the line that starts with Workspace.

For more detailed information about running tests, code style and linting, please see Running the Tests.

Submitting Incomplete Solutions

It's possible to submit an incomplete solution so you can see how others have completed the exercise.