[interpreter] add a global Python interpreter instance

dune/pybindxi/CMakeLists.txt

@@ -5,6 +5,8 @@
 # Authors:
 #   Felix Schindler (2016)
 
+dune_library_add_sources(dunepybindxi SOURCES interpreter.cc)
+
 install(FILES
         attr.h
         buffer_info.h
@@ -16,6 +18,7 @@ install(FILES
         embed.h
         eval.h
         functional.h
+        interpreter.hh
         iostream.h
         numpy.h
         operators.h

dune/pybindxi/interpreter.cc

+// This file is part of the dune-pybindxi project:
+//   https://github.com/dune-community/dune-pybindxi
+// Copyright 2009-2017 dune-xt-la developers and contributors. All rights
+// reserved.
+// License: Dual licensed as BSD 2-Clause License
+// (http://opensource.org/licenses/BSD-2-Clause)
+//      or  GPL-2.0+ (http://opensource.org/licenses/gpl-license)
+//          with "runtime exception" (http://www.dune-project.org/license.html)
+// Authors:
+//   Felix Schindler (2017)
+
+#include "interpreter.hh"
+
+namespace Dune {
+namespace PybindXI {
+
+pybind11::module
+ScopedInterpreter::import_module(const std::string &module_name) {
+  auto result = modules_.find(module_name);
+  if (result != modules_.end())
+    return result->second;
+  else {
+    modules_[module_name] = pybind11::module::import(module_name.c_str());
+    return modules_[module_name];
+  }
+} // ... load_module(...)
+
+ScopedInterpreter &GlobalInterpreter() {
+  static ScopedInterpreter global_interpreter;
+  return global_interpreter;
+}
+
+} // namespace PybindXI
+} // namespace Dune

dune/pybindxi/interpreter.hh

+// This file is part of the dune-pybindxi project:
+//   https://github.com/dune-community/dune-pybindxi
+// Copyright 2009-2017 dune-xt-la developers and contributors. All rights
+// reserved.
+// License: Dual licensed as BSD 2-Clause License
+// (http://opensource.org/licenses/BSD-2-Clause)
+//      or  GPL-2.0+ (http://opensource.org/licenses/gpl-license)
+//          with "runtime exception" (http://www.dune-project.org/license.html)
+// Authors:
+//   Felix Schindler (2017)
+
+#ifndef DUNE_PYBINDXI_INTERPRETER_HH
+#define DUNE_PYBINDXI_INTERPRETER_HH
+
+#include <map>
+#include <string>
+
+#include "embed.h"
+
+namespace Dune {
+namespace PybindXI {
+
+/**
+ * \note Most likely, you do not want to use this class directly, but
+ * GlobalInterpreter instead!
+ */
+class ScopedInterpreter {
+public:
+  pybind11::module import_module(const std::string &module_name);
+
+private:
+  pybind11::scoped_interpreter interpreter_;
+  std::map<std::string, pybind11::module> modules_;
+}; // class ScopedInterpreter
+
+ScopedInterpreter &GlobalInterpreter();
+
+} // namespace PybindXI
+} // namespace Dune
+
+#endif // DUNE_PYBINDXI_INTERPRETER_HH