examples: Add basic PythonPlugin example

examples/CMakeLists.txt

@@ -3,3 +3,4 @@ add_subdirectory(configurable_plugin)
 add_subdirectory(lua_plugin)
 add_subdirectory(multi_language_plugin)
 add_subdirectory(multi_return_lua_plugin)
+add_subdirectory(python_plugin)

examples/python_plugin/CMakeLists.txt

@@ -0,0 +1,10 @@
+add_executable(python_plugin_manager python_plugin_manager.cpp)
+target_link_libraries(python_plugin_manager PRIVATE ${LIBRARY_TARGET})
+
+add_custom_command(
+  TARGET python_plugin_manager
+  POST_BUILD
+  COMMAND ${CMAKE_COMMAND} -E copy ${CMAKE_CURRENT_SOURCE_DIR}/plugin.py
+          $<TARGET_FILE_DIR:python_plugin_manager>/plugin_1.py
+  COMMAND ${CMAKE_COMMAND} -E copy ${CMAKE_CURRENT_SOURCE_DIR}/plugin.py
+          $<TARGET_FILE_DIR:python_plugin_manager>/plugin_2.py)

examples/python_plugin/plugin.py

@@ -0,0 +1,19 @@
+import time
+
+
+def initialize(something):
+    print("initialize: ", something)
+
+
+def loop(something):
+    # this only works because of the I/O and sleep;
+    # a loop without any "non-python" operations may block all threads
+    # wanting to execute python plugins;
+    # if python 3.12 or newer is used, multiple threads can execute
+    # python code at the same time
+    while True:
+        print("loop: ", something)
+        time.sleep(1)
+
+
+print("loading")

examples/python_plugin/python_plugin_manager.cpp

@@ -0,0 +1,63 @@
+#include "plugin_manager.h"
+#include "python/plugin.h"
+
+#include <exception>
+#include <filesystem>
+#include <iostream>
+#include <thread>
+#include <tuple>
+#include <utility>
+#include <vector>
+
+int main(int argc, char* argv[])
+{
+    try {
+        if (argc < 1) {
+            return -1;
+        }
+        // path to plugins can be passed via command line;
+        // if no path was specified, the location of the executable is used instead
+        std::filesystem::path plugin_dir;
+        if (argc < 2) {
+            plugin_dir = std::filesystem::path { argv[0] }.parent_path();
+        } else {
+            plugin_dir = std::filesystem::path { argv[1] };
+        }
+        ppplugin::GenericPluginManager<ppplugin::PythonPlugin> manager;
+        std::vector<std::thread> threads;
+        int plugin_number {};
+
+        // recursively traverse filesystem to find scripts
+        const std::filesystem::recursive_directory_iterator dir_iterator { plugin_dir };
+        for (const auto& entry : dir_iterator) {
+            if (!entry.is_regular_file()) {
+                continue;
+            }
+            const auto& path = entry.path();
+            // only load files ending with ".py" and execute in separate thread
+            if (path.extension() == ".py") {
+                auto plugin = manager.loadPythonPlugin(path);
+                if (plugin) {
+                    threads.emplace_back([plugin = std::move(*plugin), plugin_number = plugin_number++]() mutable {
+                        // ignore calling errors
+                        std::ignore = plugin.call<void>("initialize", plugin_number);
+                        std::ignore = plugin.call<void>("loop", std::to_string(plugin_number));
+                    });
+                } else {
+                    std::cerr << "Failed to load " << path << '\n';
+                }
+            }
+        }
+
+        for (auto& thread : threads) {
+            thread.join();
+        }
+    } catch (const std::exception& exception) {
+        std::cerr << "A fatal error occurred: '" << exception.what() << "'\n";
+        return 1;
+    } catch (...) {
+        std::cerr << "An unknown fatal error occurred!";
+        return 1;
+    }
+    return 0;
+}