[KMS-ETH]- Enhances the singleton pattern for blockchain, adding a way to retrieve the instance.

nkms_eth/blockchain.py

@@ -13,7 +13,7 @@ class Blockchain:
     """
 
     _network = ''
-    _instance = False
+    _instance = None
 
     class AlreadyRunning(Exception):
         pass
@@ -28,10 +28,10 @@ class Blockchain:
         """
 
         # Singleton
-        if Blockchain._instance is True:
+        if Blockchain._instance is not None:
-            class_name = self.__class__.__name__
+            message = 'Blockchain: is already running. Use .get() to retrieve'.format(self._network)
-            raise Blockchain.AlreadyRunning('{} is already running. Use .get() to retrieve'.format(class_name))
+            raise Blockchain.AlreadyRunning(message)
-        Blockchain._instance = True
+        Blockchain.__instance = self
 
         if populus_config is None:
             populus_config = PopulusConfig()
@@ -43,6 +43,13 @@ class Blockchain:
         # Opens and preserves connection to a running populus blockchain
         self._chain = self._project.get_chain(self._network).__enter__()
 
+    @classmethod
+    def get(cls):
+        if cls._instance is None:
+            class_name = cls.__name__
+            raise Exception('{} has not been created.'.format(class_name))
+        return cls._instance
+
     def disconnect(self):
         self._chain.__exit__(None, None, None)
 

tests/conftest.py

@@ -10,7 +10,7 @@ def testerchain():
     chain = TesterBlockchain()
     yield chain
     del chain
-    Blockchain._instance = False
+    TesterBlockchain._instance = None
 
 
 @pytest.fixture(scope='function')