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97 lines
3.4 KiB
Markdown
97 lines
3.4 KiB
Markdown
# ETL
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We are going to do the `Transform` step of an Extract-Transform-Load.
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### ETL
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Extract-Transform-Load (ETL) is a fancy way of saying, "We have some crufty, legacy data over in this system, and now we need it in this shiny new system over here, so
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we're going to migrate this."
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(Typically, this is followed by, "We're only going to need to run this
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once." That's then typically followed by much forehead slapping and
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moaning about how stupid we could possibly be.)
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### The goal
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We're going to extract some scrabble scores from a legacy system.
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The old system stored a list of letters per score:
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- 1 point: "A", "E", "I", "O", "U", "L", "N", "R", "S", "T",
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- 2 points: "D", "G",
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- 3 points: "B", "C", "M", "P",
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- 4 points: "F", "H", "V", "W", "Y",
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- 5 points: "K",
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- 8 points: "J", "X",
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- 10 points: "Q", "Z",
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The shiny new scrabble system instead stores the score per letter, which
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makes it much faster and easier to calculate the score for a word. It
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also stores the letters in lower-case regardless of the case of the
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input letters:
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- "a" is worth 1 point.
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- "b" is worth 3 points.
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- "c" is worth 3 points.
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- "d" is worth 2 points.
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- Etc.
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Your mission, should you choose to accept it, is to transform the legacy data
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format to the shiny new format.
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### Notes
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A final note about scoring, Scrabble is played around the world in a
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variety of languages, each with its own unique scoring table. For
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example, an "E" is scored at 2 in the Māori-language version of the
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game while being scored at 4 in the Hawaiian-language version.
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## Exception messages
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Sometimes it is necessary to raise an exception. When you do this, you should include a meaningful error message to
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indicate what the source of the error is. This makes your code more readable and helps significantly with debugging. Not
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every exercise will require you to raise an exception, but for those that do, the tests will only pass if you include
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a message.
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To raise a message with an exception, just write it as an argument to the exception type. For example, instead of
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`raise Exception`, you should write:
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```python
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raise Exception("Meaningful message indicating the source of the error")
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```
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## Running the tests
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To run the tests, run the appropriate command below ([why they are different](https://github.com/pytest-dev/pytest/issues/1629#issue-161422224)):
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- Python 2.7: `py.test etl_test.py`
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- Python 3.4+: `pytest etl_test.py`
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Alternatively, you can tell Python to run the pytest module (allowing the same command to be used regardless of Python version):
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`python -m pytest etl_test.py`
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### Common `pytest` options
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- `-v` : enable verbose output
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- `-x` : stop running tests on first failure
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- `--ff` : run failures from previous test before running other test cases
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For other options, see `python -m pytest -h`
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## Submitting Exercises
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Note that, when trying to submit an exercise, make sure the solution is in the `$EXERCISM_WORKSPACE/python/etl` directory.
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You can find your Exercism workspace by running `exercism debug` and looking for the line that starts with `Workspace`.
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For more detailed information about running tests, code style and linting,
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please see [Running the Tests](http://exercism.io/tracks/python/tests).
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## Source
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The Jumpstart Lab team [http://jumpstartlab.com](http://jumpstartlab.com)
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## Submitting Incomplete Solutions
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It's possible to submit an incomplete solution so you can see how others have completed the exercise.
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