python-constraint 1.3

python-constraint is a module implementing support for handling CSPs (Constraint Solving Problems) over finite domain

|Build Status| |Code Health| |Code Coverage|

python-constraint
=================

Introduction
-----------
The Python constraint module offers solvers for Constraint Solving Problems (CSPs) over finite domains in simple and pure Python. CSP is class of problems which may be represented in terms of variables (a, b, ...), domains (a in [1, 2, 3], ...), and constraints (a < b, ...).

Examples
--------

Basics
~~~~~~

This interactive Python session demonstrates the module basic operation:

.. code-block:: python

>>> from constraint import *
>>> problem = Problem()
>>> problem.addVariable("a", [1,2,3])
>>> problem.addVariable("b", [4,5,6])
>>> problem.getSolutions()
[{'a': 3, 'b': 6}, {'a': 3, 'b': 5}, {'a': 3, 'b': 4},
{'a': 2, 'b': 6}, {'a': 2, 'b': 5}, {'a': 2, 'b': 4},
{'a': 1, 'b': 6}, {'a': 1, 'b': 5}, {'a': 1, 'b': 4}]

>>> problem.addConstraint(lambda a, b: a*2 == b,
("a", "b"))
>>> problem.getSolutions()
[{'a': 3, 'b': 6}, {'a': 2, 'b': 4}]

>>> problem = Problem()
>>> problem.addVariables(["a", "b"], [1, 2, 3])
>>> problem.addConstraint(AllDifferentConstraint())
>>> problem.getSolutions()
[{'a': 3, 'b': 2}, {'a': 3, 'b': 1}, {'a': 2, 'b': 3},
{'a': 2, 'b': 1}, {'a': 1, 'b': 2}, {'a': 1, 'b': 3}]

Rooks problem
~~~~~~~~~~~~~

The following example solves the classical Eight Rooks problem:

.. code-block:: python

>>> problem = Problem()
>>> numpieces = 8
>>> cols = range(numpieces)
>>> rows = range(numpieces)
>>> problem.addVariables(cols, rows)
>>> for col1 in cols:
... for col2 in cols:
... if col1 < col2:
... problem.addConstraint(lambda row1, row2: row1 != row2,
... (col1, col2))
>>> solutions = problem.getSolutions()
>>> solutions
>>> solutions
[{0: 7, 1: 6, 2: 5, 3: 4, 4: 3, 5: 2, 6: 1, 7: 0},
{0: 7, 1: 6, 2: 5, 3: 4, 4: 3, 5: 2, 6: 0, 7: 1},
{0: 7, 1: 6, 2: 5, 3: 4, 4: 3, 5: 1, 6: 2, 7: 0},
{0: 7, 1: 6, 2: 5, 3: 4, 4: 3, 5: 1, 6: 0, 7: 2},
...
{0: 7, 1: 5, 2: 3, 3: 6, 4: 2, 5: 1, 6: 4, 7: 0},
{0: 7, 1: 5, 2: 3, 3: 6, 4: 1, 5: 2, 6: 0, 7: 4},
{0: 7, 1: 5, 2: 3, 3: 6, 4: 1, 5: 2, 6: 4, 7: 0},
{0: 7, 1: 5, 2: 3, 3: 6, 4: 1, 5: 4, 6: 2, 7: 0},
{0: 7, 1: 5, 2: 3, 3: 6, 4: 1, 5: 4, 6: 0, 7: 2},
...]


Magic squares
~~~~~~~~~~~~~

This example solves a 4x4 magic square:

.. code-block:: python

>>> problem = Problem()
>>> problem.addVariables(range(0, 16), range(1, 16 + 1))
>>> problem.addConstraint(AllDifferentConstraint(), range(0, 16))
>>> problem.addConstraint(ExactSumConstraint(34), [0, 5, 10, 15])
>>> problem.addConstraint(ExactSumConstraint(34), [3, 6, 9, 12])
>>> for row in range(4):
... problem.addConstraint(ExactSumConstraint(34),
[row * 4 + i for i in range(4)])
>>> for col in range(4):
... problem.addConstraint(ExactSumConstraint(34),
[col + 4 * i for i in range(4)])
>>> solutions = problem.getSolutions()

Features
--------

The following solvers are available:

- Backtracking solver
- Recursive backtracking solver
- Minimum conflicts solver


.. role:: python(code)
:language: python

Predefined constraint types currently available:

- :python:`FunctionConstraint`
- :python:`AllDifferentConstraint`
- :python:`AllEqualConstraint`
- :python:`ExactSumConstraint`
- :python:`MaxSumConstraint`
- :python:`MinSumConstraint`
- :python:`InSetConstraint`
- :python:`NotInSetConstraint`
- :python:`SomeInSetConstraint`
- :python:`SomeNotInSetConstraint`

API documentation
-----------------
Documentation for the module is available at: <http://labix.org/doc/constraint/>

Download
--------
New version (Python 2 & 3)
~~~~~~~~~~~

.. code-block:: python

$ pip install git+https://github.com/python-constraint/python-constraint.git

Old version (v 1.2 - Python 2 only)
~~~~~~~~~~~
Download the module at the Python Package Index: <https://pypi.python.org/pypi/python-constraint>


Original code / information
---------------------------

Code was taken from https://pypi.python.org/pypi/python-constraint/1.2
(2014-04-04)

See https://labix.org/python-constraint

Roadmap
-------

This GitHub organization and repository is a global effort to help to
maintain python-constraint

- Create some unit tests - DONE
- Enable continuous integration - DONE
- Port to Python 3 (Python 2 being also supported) - DONE
- Respect Style Guide for Python Code (PEP8) - DONE
- Improve code coverage writting more unit tests - ToDo
- Move doc to Sphinx or MkDocs - https://readthedocs.org/ - ToDo

Contact
-------
- Gustavo Niemeyer <[e-mail]>
- Sébastien Celles <[e-mail]>

But it's probably better to open an issue <https://github.com/python-constraint/python-constraint/issues>


.. |Build Status| image:: https://travis-ci.org/python-constraint/python-constraint.svg?branch=unit_tests
:target: https://travis-ci.org/python-constraint/python-constraint
.. |Code Health| image:: https://landscape.io/github/python-constraint/python-constraint/master/landscape.svg?style=flat
:target: https://landscape.io/github/python-constraint/python-constraint/master
:alt: Code Health
.. |Code Coverage| image:: https://coveralls.io/repos/github/python-constraint/python-constraint/badge.svg
:target: https://coveralls.io/github/python-constraint/python-constraint