python_version: cache for performance

This allows allows force_old to be cached

Author: scivision

+stdlib/python_version.m

@@ -1,19 +1,33 @@
 %% PYTHON_VERSION get the Python version used by MATLAB
 %
-%## Output
-%* 1x3 vector of major, minor, micro version e.g. Python 3.14.2 = [3, 14, 2]
+% uses persistent variable to cache the Python version
+%
+%%% Inputs
+% * force_old: (optional) boolean flag to force checking of Python on Matlab < R2022a
+%
+%%% Output
+% * v: 1x3 vector of major, minor, micro version e.g. Python 3.14.2 = [3, 14, 2]
+%
 % we need to do at least one Python function call to handle cases
 % where the environment has changed since pyenv() was set. For example
 % HPC with "module load python3..."
 
-function v = python_version(force)
+function v = python_version(force_old)
 arguments
-  force (1,1) logical = false
+  force_old (1,1) logical = false
+end
+
+persistent v_
+
+if ~isempty(v_)
+  v = v_;
+  return
 end
 
 v = [];
 
-if isMATLABReleaseOlderThan('R2022a') && ~force
+% For MATLAB versions older than R2022a, skip Python version check unless force_old is true
+if isMATLABReleaseOlderThan('R2022a') && ~force_old
   return
 end
 
@@ -22,4 +36,9 @@
 
 v = pvt_get_python_version();
 
+% cache the result
+if ~isempty(v)
+  v_ = v;
+end
+
 end