pyscf.semiemprical import not required unless needed at runtime (#170)

* Skip test and import if pyscf.semiempirical is not installed.

Co-authored-by: Valentin Senicourt <valentin.senicourt@1qbit.com>
Co-authored-by: ValentinS4t1qbit <41597680+ValentinS4t1qbit@users.noreply.github.com>

tangelo/algorithms/classical/semi_empirical_solver.py

@@ -30,8 +30,7 @@
     - MINDO3
 """
 
-from pyscf.semiempirical import mindo3
-
+from tangelo.helpers.utils import is_package_installed
 from tangelo.algorithms.electronic_structure_solver import ElectronicStructureSolver
 
 
@@ -50,6 +49,9 @@ class MINDO3Solver(ElectronicStructureSolver):
     """
 
     def __init__(self, molecule):
+        if not is_package_installed("pyscf.semiempirical"):
+            raise ModuleNotFoundError(f"The pyscf.semiempirical module is not available and is required by {self.__class__.__name__}.")
+
         self.molecule = molecule
 
     def simulate(self):
@@ -58,6 +60,7 @@ def simulate(self):
         Returns:
             float: RMINDO3 energy.
         """
+        from pyscf.semiempirical import mindo3
 
         solver = mindo3.RMINDO3(self.molecule.to_pyscf()).run(verbose=0)
         total_energy = solver.e_tot

tangelo/algorithms/classical/tests/test_semi_empirical_solver.py

@@ -14,20 +14,22 @@
 
 import unittest
 
+from tangelo.helpers.utils import is_package_installed
 from tangelo.molecule_library import mol_pyridine
-from tangelo.algorithms.classical.semi_empirical_solver import MINDO3Solver
 
 
-class MINDO3SolverTest(unittest.TestCase):
+class SemiEmpiricalSolverTest(unittest.TestCase):
 
-    def test_energy(self):
+    @unittest.skipIf(not is_package_installed("pyscf.semiempirical"), "Test Skipped: pyscf.semiempirical module not available \n")
+    def test_mindo3_energy(self):
         """Test MINDO3Solver with pyridine. Validated with:
             - MINDO/3-derived geometries and energies of alkylpyridines and the
             related N-methylpyridinium cations. Jeffrey I. Seeman,
             John C. Schug, and Jimmy W. Viers
             The Journal of Organic Chemistry 1983 48 (14), 2399-2407
             DOI: 10.1021/jo00162a021.
         """
+        from tangelo.algorithms.classical import MINDO3Solver
 
         solver = MINDO3Solver(mol_pyridine)
         energy = solver.simulate()