core is a singleton

process_bigraph/__init__.py

@@ -3,9 +3,11 @@
 from process_bigraph.processes import register_processes
 from process_bigraph.composite import Process, Step, Composite, ProcessTypes, interval_time_precision
 
-
 pretty = pprint.PrettyPrinter(indent=2)
 
+# make the singleton instance of the ProcessTypes class
+core = ProcessTypes()
+
 
 def pp(x):
     """Print ``x`` in a pretty format."""

process_bigraph/composite.py

@@ -251,18 +251,27 @@ class ProcessTypes(TypeSystem):
     It maintains a registry of process types and provides methods to register
     new process types, protocols, and emitters.
     """
+    _instance = None  # Class-level private variable for the singleton instance
 
-    def __init__(self):
-        super().__init__()
-        self.process_registry = Registry()
-        self.protocol_registry = Registry()
+    def __new__(cls, *args, **kwargs):
+        if cls._instance is None:
+            cls._instance = super(ProcessTypes, cls).__new__(cls)
+            # Initialize the instance
+            cls._instance._is_initialized = False
+        return cls._instance
 
-        self.register_types(PROCESS_TYPES)
-        self.register_protocols(BASE_PROTOCOLS)
-        self.register_processes(BASE_EMITTERS)
+    def __init__(self):
+        if not self._is_initialized:  # Prevent re-initialization
+            super().__init__()
+            self.process_registry = Registry()
+            self.protocol_registry = Registry()
 
-        self.register_process('composite', Composite)
+            self.register_types(PROCESS_TYPES)
+            self.register_protocols(BASE_PROTOCOLS)
+            self.register_processes(BASE_EMITTERS)
 
+            self.register_process('composite', Composite)
+            self._is_initialized = True
 
     def register_protocols(self, protocols):
         """Register protocols with the core"""

process_bigraph/tests.py

@@ -731,6 +731,13 @@ def test_stochastic_deterministic_composite(core):
     pass
 
 
+def test_singleton_core():
+    from process_bigraph import core
+    from process_bigraph import ProcessTypes
+    core2 = ProcessTypes()  # This should point to the singleton instance
+    assert core is core2, "ProcessTypes is not behaving like a singleton."
+
+
 if __name__ == '__main__':
     core = ProcessTypes()
     core = register_types(core)