`1` ```exercism fetch python variable-length-quantity ```

Variable Length Quantity

Implement variable length quantity encoding and decoding.

The goal of this exercise is to implement VLQ encoding/decoding.

In short, the goal of this encoding is to encode integer values in a way that would save bytes. Only the first 7 bits of each byte is significant (right-justified; sort of like an ASCII byte). So, if you have a 32-bit value, you have to unpack it into a series of 7-bit bytes. Of course, you will have a variable number of bytes depending upon your integer. To indicate which is the last byte of the series, you leave bit #7 clear. In all of the preceding bytes, you set bit #7.

So, if an integer is between `0-127`, it can be represented as one byte. Although VLQ can deal with numbers of arbitrary sizes, for this exercise we will restrict ourselves to only numbers that fit in a 32-bit unsigned integer. Here are examples of integers as 32-bit values, and the variable length quantities that they translate to:

 ```1 2 3 4 5 6 7 8 9 10 11 12 13``` ``` NUMBER VARIABLE QUANTITY 00000000 00 00000040 40 0000007F 7F 00000080 81 00 00002000 C0 00 00003FFF FF 7F 00004000 81 80 00 00100000 C0 80 00 001FFFFF FF FF 7F 00200000 81 80 80 00 08000000 C0 80 80 00 0FFFFFFF FF FF FF 7F ```

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:

 `1` ```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 variable_length_quantity_test.py`
• Python 3.4+: `pytest variable_length_quantity_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 variable_length_quantity_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/variable-length-quantity` 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 the help page.

Source

A poor Splice developer having to implement MIDI encoding/decoding. https://splice.com

Submitting Incomplete Solutions

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