From 3b1244831e826b0a6ebe9163d138f4c91aecda8e Mon Sep 17 00:00:00 2001
From: Richard Berger <richard.berger@temple.edu>
Date: Fri, 27 Mar 2020 16:28:43 -0400
Subject: [PATCH] Add Python::has_minimum_version

---
 src/KIM/kim_property.cpp   | 18 +++++++-----------
 src/PYTHON/python_impl.cpp |  7 +++++++
 src/PYTHON/python_impl.h   |  1 +
 src/lmppython.cpp          |  8 ++++++++
 src/lmppython.h            |  2 ++
 5 files changed, 25 insertions(+), 11 deletions(-)

diff --git a/src/KIM/kim_property.cpp b/src/KIM/kim_property.cpp
index 0a55d6aae9..d2f1d145c9 100644
--- a/src/KIM/kim_property.cpp
+++ b/src/KIM/kim_property.cpp
@@ -75,24 +75,20 @@ using namespace LAMMPS_NS;
 
 kimProperty::kimProperty(LAMMPS *lmp) : Pointers(lmp)
 {
-#if LMP_PYTHON
-#if PY_MAJOR_VERSION != 3
-  error->all(FLERR, "Invalid Python version.\n"
-                    "The kim-property Python package requires Python "
-                    "3 >= 3.6 support.");
-#endif
   // one-time initialization of Python interpreter
   python->init();
-#else
-  error->all(FLERR, "Error Python support missing! Compile with PYTHON "
-                    "package installed!");
-#endif // LMP_PYTHON
+
+  if (!python->has_minimum_version(3, 6)) {
+    error->all(FLERR, "Invalid Python version.\n"
+                      "The kim-property Python package requires Python "
+                      "3 >= 3.6 support.");
+  }
 }
 
 void kimProperty::command(int narg, char **arg)
 {
 #if LMP_PYTHON
-#if PY_MAJOR_VERSION == 3
+#if PY_MAJOR_VERSION >= 3
   if (narg < 2)
     error->all(FLERR, "Invalid `kim_property` command.");
 
diff --git a/src/PYTHON/python_impl.cpp b/src/PYTHON/python_impl.cpp
index 1188942e75..e027079f1f 100644
--- a/src/PYTHON/python_impl.cpp
+++ b/src/PYTHON/python_impl.cpp
@@ -535,3 +535,10 @@ void PythonImpl::deallocate(int i)
   delete [] pfuncs[i].ovarname;
   delete [] pfuncs[i].longstr;
 }
+
+/* ------------------------------------------------------------------ */
+
+bool PythonImpl::has_minimum_version(int major, int minor)
+{
+    return (PY_MAJOR_VERSION == major && PY_MINOR_VERSION >= minor) || (PY_MAJOR_VERSION > major);
+}
diff --git a/src/PYTHON/python_impl.h b/src/PYTHON/python_impl.h
index f890f54f3b..2fd52b8ead 100644
--- a/src/PYTHON/python_impl.h
+++ b/src/PYTHON/python_impl.h
@@ -32,6 +32,7 @@ class PythonImpl : protected Pointers, public PythonInterface {
   char *long_string(int);
   int execute_string(char *);
   int execute_file(char *);
+  bool has_minimum_version(int major, int minor);
 
  private:
   int ninput,noutput,length_longstr;
diff --git a/src/lmppython.cpp b/src/lmppython.cpp
index 52abd93f10..132790bdbe 100644
--- a/src/lmppython.cpp
+++ b/src/lmppython.cpp
@@ -117,3 +117,11 @@ int Python::execute_file(char *fname)
   init();
   return impl->execute_file(fname);
 }
+
+/* ------------------------------------------------------------------ */
+
+bool Python::has_minimum_version(int major, int minor)
+{
+  init();
+  return impl->has_minimum_version(major, minor);
+}
diff --git a/src/lmppython.h b/src/lmppython.h
index 3d55c4827b..fab307d9e6 100644
--- a/src/lmppython.h
+++ b/src/lmppython.h
@@ -28,6 +28,7 @@ public:
   virtual char * long_string(int ifunc) = 0;
   virtual int execute_string(char *) = 0;
   virtual int execute_file(char *) = 0;
+  virtual bool has_minimum_version(int major, int minor) = 0;
 };
 
 class Python : protected Pointers {
@@ -42,6 +43,7 @@ public:
   char * long_string(int ifunc);
   int execute_string(char *);
   int execute_file(char *);
+  bool has_minimum_version(int major, int minor);
 
   bool is_enabled() const;
   void init();