add singleton

Author: Jeeven Dhanoa

app/data/__init__.py

@@ -2,9 +2,10 @@
 from ..services.location.csbs import CSBSLocationService
 from ..services.location.jhu import JhuLocationService
 from ..services.location.nyt import NYTLocationService
+from ..utils.singleton import Singleton
 
 
-class DataSources:
+class DataSources(Singleton):
     """
     Class to represent the root of the aggregate containing the location services.
     """
@@ -16,9 +17,16 @@ class DataSources:
         "nyt": NYTLocationService(),
     }
 
+    __instance = None
+
     def __init__(self):
         pass
 
+    def get_instance():
+        if DataSources.__instance is None:
+            DataSources.__instance = DataSources()
+        return DataSources.__instance
+
     def get_data_source(self, source):
         """
         Retrieves the provided data-source service.

app/main.py

@@ -41,7 +41,7 @@
     on_shutdown=[teardown_client_session],
 )
 
-DATA_SOURCES = DataSources()
+DATA_SOURCES = DataSources.get_instance()
 
 # #####################
 # Middleware

app/routers/v2.py

@@ -7,7 +7,7 @@
 from ..models import LatestResponse, LocationResponse, LocationsResponse
 
 V2 = APIRouter()
-DATA_SOURCES = DataSources()
+DATA_SOURCES = DataSources.get_instance()
 
 
 class Sources(str, enum.Enum):

app/utils/singleton.py

@@ -0,0 +1,11 @@
+class Singleton(object):
+    def __new__(cls, *args, **kwds):
+        it = cls.__dict__.get("__it__")
+        if it is not None:
+            return it
+        cls.__it__ = it = object.__new__(cls)
+        it.init(*args, **kwds)
+        return it
+
+    def init(self, *args, **kwds):
+        pass