Create a custom set type.

Sometimes it is necessary to define a custom data structure of some type, like a set. In this exercise you will define your own set. How it works internally doesn't matter, as long as it behaves like a set of unique elements.

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")

To run the tests, run pytest custom_set_test.py

Alternatively, you can tell Python to run the pytest module: python -m pytest custom_set_test.py

• -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

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

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