extypes 0.1.0

extypes
=======

This project provides a few enhanced types for Python:

* A "constrained set" (ordered or not)
* That's all for now.


It also provides extensions for Django.


It has been fully tested with all versions of Python from 2.6 to 3.4; and is distributed under the BSD license.


Links
-----

* Package on PyPI: http://pypi.python.org/pypi/extypes
* Repository and issues on GitHub: http://github.com/rbarrois/extypes
* Doc on http://readthedocs.org/docs/extypes/


Getting started
---------------

Intall the package from `PyPI`_, using pip:

.. code-block:: sh

$ pip install extypes

Or from GitHub:

.. code-block:: sh

$ git clone git://github.com/rbarrois/extypes
$ cd extypes
$ python setup.py install


To check that everything went fine, fire a Python shell and import ``extypes``:


.. code-block:: python

import extypes


Introduction
------------

.. currentmodule:: extypes

``extypes`` provides a new type, ``ConstrainedSet``.

This is a ``set()``-like object, but values can only be taken from a
specific set of options.


A ``ConstrainedSet`` is declared in a manner very similar to :class:`collections.namedtuple`:

.. code-block:: python

import extypes
Foods = extypes.ConstrainedSet(['eggs', 'spam', 'bacon'])

This will declare a new class, ``Foods``, whose instances are ``ConstrainedSet`` that only accept
options among ``'eggs'``, ``'spam'`` and ``'bacon'``.


Those objects can be used as simple ``set()`` objects:

.. code-block:: pycon

>>> import extypes
>>> Foods = extypes.ConstrainedSet(['eggs', 'spam', 'bacon'])
>>> meat = Foods(['spam', 'bacon'])
>>> fresh = Foods(['bacon', 'eggs'])
>>> 'eggs' in meat
False
>>> 'eggs' in fresh
True
>>> meat & fresh
Foods(['bacon'])

As a ``set()`` object, they are mutable:

.. code-block:: pycon

>>> import extypes
>>> Foods = extypes.ConstrainedSet(['eggs', 'spam', 'bacon'])
>>> meat = Foods(['spam', 'bacon'])
>>> meat.remove('spam')
>>> meat
Foods(['bacon'])

And iterable:

.. code-block:: pycon

>>> import extypes
>>> Foods = extypes.ConstrainedSet(['eggs', 'spam', 'bacon'])
>>> meat = Foods(['bacon', 'spam'])
>>> list(meat)
['spam', 'bacon']

But only valid options are accepted:

.. code-block:: pycon

>>> Foods = extypes.ConstrainedSet(['eggs', 'spam', 'bacon'])
>>> greens = Foods(['spinach']
Traceback (most recent call last):
...
ValueError: Invalid keys ['spinach'], please use a value in ['spam', 'bacon', 'eggs'].


Extensions: Django
------------------

.. currentmodule:: extypes.django

``extypes`` also provides custom fields for Django - compatible with Django 1.6 and upwards.

.. code-block:: python

from django.db import models
import extypes
import extypes.django

Foods = extypes.ConstrainedSet(['eggs', 'spam', 'bacon'])

class Fridge(models.Model):
contents = extypes.django.SetField(choices=Foods)

This field will simply behave as a simple ``ConstrainedSet``.

.. code-block:: pycon

>>> fridge = Fridge(contents=['bacon'])
>>> fridge.contents.add('eggs')
>>> fridge.save()


It is displayed in forms as a multiple choice field.
In the database, it is saved as a ``|``-separated list of enabled values
(in the above example, the field is stored as ``|eggs|bacon|``).