Implement run-length encoding and decoding.
Run-length encoding (RLE) is a simple form of data compression, where runs (consecutive data elements) are replaced by just one data value and count.
For example we can represent the original 53 characters with only 13.
"WWWWWWWWWWWWBWWWWWWWWWWWWBBBWWWWWWWWWWWWWWWWWWWWWWWWB" -> "12WB12W3B24WB"
RLE allows the original data to be perfectly reconstructed from the compressed data, which makes it a lossless data compression.
"AABCCCDEEEE" -> "2AB3CD4E" -> "AABCCCDEEEE"
For simplicity, you can assume that the unencoded string will only contain the letters A through Z (either lower or upper case) and whitespace. This way data to be encoded will never contain any numbers and numbers inside data to be decoded always represent the count for the following character.
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 run_length_encoding_test.py
Alternatively, you can tell Python to run the pytest module:
python -m pytest run_length_encoding_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/run-length-encoding 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.
Wikipedia https://en.wikipedia.org/wiki/Run-length_encoding
It's possible to submit an incomplete solution so you can see how others have completed the exercise.