Velocity Reviews > ANN: python-constraint 1.0

# ANN: python-constraint 1.0

Gustavo Niemeyer
Guest
Posts: n/a

 07-07-2005
--------
Overview
--------

**python-constraint** [1]_ is a Python module offering 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`, ...).

... [1] http://codespeak.net/~niemeyer/constraint/

--------
Examples
--------

Basic
-----

Here is a basic interactive example::

>>> from constraint import *
>>> problem = Problem()
>>> 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.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
-----

Here is an example solving the classical rooks problem::

problem = Problem()
numpieces = 8
cols = range(numpieces)
rows = range(numpieces)
for col1 in cols:
for col2 in cols:
if col1 < col2:
problem.addConstraint(lambda row1, row2: row1 != row2,
(col1, col2))
solutions = problem.getSolutions()

Magic squares
-------------

And here is an example solving a 4x4 magic square::

problem = Problem()
for row in range(4):
[row*4+i for i in range(4)])
for col in range(4):
[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

Predefined constraint types currently available:

- FunctionConstraint
- AllDifferentConstraint
- AllEqualConstraint
- ExactSumConstraint
- MaxSumConstraint
- MinSumConstraint
- InSetConstraint
- NotInSetConstraint
- SomeInSetConstraint
- SomeNotInSetConstraint

-------------
Documentation
-------------

There's documentation for the module at:

- http://codespeak.net/~niemeyer/constraint/doc/

--------
--------

**python-constraint** may be found at the following

- http://codespeak.net/~niemeyer/constraint/files/

---------------------
Subversion repository
---------------------

Available at:

- http://codespeak.net/svn/user/niemeyer/constraint/

--
Gustavo Niemeyer
http://niemeyer.net

gabriele renzi
Guest
Posts: n/a

 07-07-2005
Gustavo Niemeyer ha scritto:
> --------
> Overview
> --------
>
> **python-constraint** [1]_ is a Python module offering 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`, ...).

This sound cool, but have you noticed logilab.constraint? Care to contrast?