python-constraint · fjwillemsen · Feb 11, 2025 · Jan 30, 2025 · Jan 30, 2025 · Jan 31, 2025
diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -2,13 +2,21 @@
 
 ## Python Constraint
 
-All notable changes to this code base will be documented in this file, for every released major and minor version.
+All notable changes to this code base will be documented in this file, for every released major and minor version. For all versions, see [releases](https://github.com/python-constraint/python-constraint/releases). 
+
+### Version 2.1.0
+
+- Released: TBD
+- Issues / Enhancements:
+  - Implemented a new string format for constraints, that is automatically parsed to constraint types (currently in beta, please report issues)
+  - Implemented a new `ParallelSolver` with both Thread and Process mode (currently experimental)
+  - Added Python 3.13 and experimental 3.14 support
 
 ### Version 2.0.0
 
 - Released: 2025-01-29
 - Maintainer: Floris-Jan Willemsen <[email protected]>
-- Issues/Enhancements:
+- Issues / Enhancements:
   - Cythonized the package
   - Added the `OptimizedBacktracking` solver based on [issue #62](https://github.com/python-constraint/python-constraint/issues/62)
   - Added type-hints to improve Cythonization
@@ -30,7 +38,7 @@ All notable changes to this code base will be documented in this file, for every
 ### Version 1.4.0
 
 - Released: 2018-11-05
-- Issues/Enhancements:
+- Issues / Enhancements:
   - Add tests around `SomeNotInSetConstraint.`
   - Minor `README` fixes
   - Fix `dict.keys()` issue with Python 3 and add some unit tests
@@ -39,14 +47,14 @@ All notable changes to this code base will be documented in this file, for every
 ### Version 1.3.1
 
 - Released: 2017-03-31
-- Issues/Enhancements:
+- Issues / Enhancements:
   - Better `README` rendering (using reStructuredText)
 
 ### Version 1.3
 
 - Released: 2017-03-31
 - Maintainer: Sébastien Celles <[email protected]>
-- Issues/Enhancements:
+- Issues / Enhancements:
   - Original code forked from https://labix.org/python-constraint
   - Publish on Github
   - Python 2 / 3 support

diff --git a/README.rst b/README.rst
@@ -12,6 +12,11 @@ python-constraint
 | For an overview of recent changes, visit the `Changelog <https://github.com/python-constraint/python-constraint/blob/main/CHANGELOG.md>`_.
 | The complete documentation can be found `here <http://python-constraint.github.io/python-constraint/>`_.
 
+| New: writing constraints in the new string format is preferable over functions and lambdas. 
+| These strings, even as compound statements, are automatically parsed to faster built-in constraints, are more concise, and do not require constraint solving familiarity by the user to be efficient.
+| For example, :code:`problem.addConstraint(["50 <= x * y < 100"])` is parsed to :code:`[MinProdConstraint(50, ["x", "y"]), MaxProdConstraint(100, ["x", "y"])]`. 
+| This feature is in beta and subject to possible change, please provide feedback.
+
 .. contents::
     :local:
     :depth: 1
@@ -40,8 +45,7 @@ This interactive Python session demonstrates basic operations:
      {'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.addConstraint("a*2 == b") # string constraints are preferable over the black-box problem.addConstraint(lambda a, b: a*2 == b, ("a", "b"))
     >>> problem.getSolutions()
     [{'a': 3, 'b': 6}, {'a': 2, 'b': 4}]
 
@@ -114,6 +118,7 @@ The following solvers are available:
 - Optimized backtracking solver
 - Recursive backtracking solver
 - Minimum conflicts solver
+- Parallel solver
 
 .. role:: python(code)
    :language: python
@@ -168,8 +173,6 @@ For an overview of recent changes, visit the `Changelog <https://github.com/pyth
 
 Planned development:
 
-- Add a string parser for constraints
-- Add parallel-capable solver
 - Add `benchmarking tests <https://pypi.org/project/pytest-benchmark/>`_ automated with `GH actions <https://github.com/benchmark-action/github-action-benchmark>`_
 - Versioned documentation
 

diff --git a/constraint/__init__.py b/constraint/__init__.py
@@ -31,6 +31,7 @@
 from constraint.domain import *   # noqa: F403
 from constraint.constraints import *  # noqa: F403
 from constraint.solvers import *   # noqa: F403
+from constraint.parser import * # noqa: F403
 
 if __name__ == "__main__":
     from tests import test_doctests

diff --git a/constraint/constraints.c b/constraint/constraints.c
diff --git a/constraint/constraints.py b/constraint/constraints.py
@@ -186,6 +186,16 @@ def __call__(  # noqa: D102
                 not forwardcheck or missing != 1 or self.forwardCheck(variables, domains, assignments)
             )
         return self._func(*parms)
+
+class CompilableFunctionConstraint(Constraint):
+    """Wrapper function for picklable string constraints that must be compiled into a FunctionConstraint later on."""
+
+    def __init__(self, func: str, assigned: bool = True):     # noqa: D102, D107
+        self._func = func
+        self._assigned = assigned
+
+    def __call__(self, variables, domains, assignments, forwardcheck=False, _unassigned=Unassigned):   # noqa: D102
+        raise NotImplementedError("CompilableFunctionConstraint can not be called directly")
 
 
 class AllDifferentConstraint(Constraint):

diff --git a/constraint/domain.c b/constraint/domain.c