say / cardinal number exercise

python/say/README.md

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+# Say
+
+Given a number from 0 to 999,999,999,999, spell out that number in English.
+
+## Step 1
+
+Handle the basic case of 0 through 99.
+
+If the input to the program is `22`, then the output should be
+`'twenty-two'`.
+
+Your program should complain loudly if given a number outside the
+blessed range.
+
+Some good test cases for this program are:
+
+- 0
+- 14
+- 50
+- 98
+- -1
+- 100
+
+### Extension
+
+If you're on a Mac, shell out to Mac OS X's `say` program to talk out
+loud. If you're on Linux or Windows, eSpeakNG may be available with the command `espeak`.
+
+## Step 2
+
+Implement breaking a number up into chunks of thousands.
+
+So `1234567890` should yield a list like 1, 234, 567, and 890, while the
+far simpler `1000` should yield just 1 and 0.
+
+The program must also report any values that are out of range.
+
+## Step 3
+
+Now handle inserting the appropriate scale word between those chunks.
+
+So `1234567890` should yield `'1 billion 234 million 567 thousand 890'`
+
+The program must also report any values that are out of range.  It's
+fine to stop at "trillion".
+
+## Step 4
+
+Put it all together to get nothing but plain English.
+
+`12345` should give `twelve thousand three hundred forty-five`.
+
+The program must also report any values that are out of range.
+
+### Extensions
+
+Use _and_ (correctly) when spelling out the number in English:
+
+- 14 becomes "fourteen".
+- 100 becomes "one hundred".
+- 120 becomes "one hundred and twenty".
+- 1002 becomes "one thousand and two".
+- 1323 becomes "one thousand three hundred and twenty-three".
+
+## 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:
+
+```python
+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](https://github.com/pytest-dev/pytest/issues/1629#issue-161422224)):
+
+- Python 2.7: `py.test say_test.py`
+- Python 3.4+: `pytest say_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 say_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/say` 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](http://exercism.io/tracks/python/tests).
+
+## Source
+
+A variation on JavaRanch CattleDrive, exercise 4a [http://www.javaranch.com/say.jsp](http://www.javaranch.com/say.jsp)
+
+## Submitting Incomplete Solutions
+
+It's possible to submit an incomplete solution so you can see how others have completed the exercise.