Correctly working singleton for configuration

Update the way the 'singleton' decorator works. Now aims to result in a
single state, not a single instance. The previous design pattern caused
problems in testing (we maintained a single instance of `config`
throughout the entire test suite, which led to test failure when running
test_config - the `config` instance was instantiated in KDEOrigin.

StatInterface/KDEOrigin.py

@@ -79,12 +79,12 @@ def __init__(self, configFile, gridLimit, kdeStep, lonLat=None,
         self.cz = None
 
         self.configFile = configFile
-        config = ConfigParser()
-        config.read(configFile)
+        self.config = ConfigParser()
+        self.config.read(configFile)
 
         if lonLat is None:
             # Load the data from file:
-            self.outputPath = config.get('Output', 'Path')
+            self.outputPath = self.config.get('Output', 'Path')
             self.processPath = pjoin(self.outputPath, 'process')
             LOGGER.debug("Loading " + pjoin(self.processPath, 'init_lon_lat'))
             ll = flLoadFile(pjoin(self.processPath, 'init_lon_lat'), '%', ',')

Utilities/config.py

@@ -231,23 +231,27 @@ def formatList(lst):
 filename=slp.day.ltm.nc
 
 """
-
-
 def singleton(cls):
-    instances = {}
-
-    def getinstance(*args, **kwargs):
-        """
-        Retrieve an instance of a class. If one (instantiated with
-        the provided args & kwargs) does not exist, then 
-        create an instance and return it.
-        """
-
-        if cls not in instances:
-            instances[cls] = cls(*args, **kwargs)
-        return instances[cls]
-    return getinstance
+    """
+    Actually a Borg!
+    Ensure only a single state for all instances of the class
+    
+    See http://code.activestate.com/recipes/66531/#c30 - I added the _drop() 
+    method to permit clean up in testing frameworks.
 
+    """
+    cls._state = {}
+    originit = cls.__init__
+    def newinit(self, *args, **kwargs):
+        self.__dict__ = cls._state
+        originit(self, *args, **kwargs)
+    def _drop(self):
+        cls._state = {}
+        self.__dict__ = {}
+
+    cls._drop = _drop
+    cls.__init__ = newinit
+    return cls
 
 @singleton
 class ConfigParser(RawConfigParser):
@@ -262,7 +266,7 @@ def __init__(self, defaults=DEFAULTS):
         RawConfigParser.__init__(self)
         self.readfp(io.BytesIO(defaults))
         self.readonce = False
-
+        
     def geteval(self, section, option):
         """
         :param str section: Section name to evaluate.

tests/test_KDEOrigin.py

@@ -32,6 +32,9 @@ def setUp(self):
         lonLat = cPickle.load(open(os.path.join(unittest_dir, 'test_data', 'kde_origin_lonLat.pck')))
         self.kdeOrigin = KDEOrigin.KDEOrigin(None, gridLimit, kdeStep, lonLat)
 
+    def tearDown(self):
+        self.kdeOrigin.config._drop()
+
     def test_GenerateKDE(self):
         """Testing GenerateKDE for 2D data"""
         pkl_file = open(os.path.join(unittest_dir, 'test_data', 'kdeOrigin_xyz.pck'), 'r')

tests/test_config.py

@@ -43,7 +43,10 @@ def setUp(self):
         self.evalopt = {'x':1.0,'y':0.5}
         self.listopt1 = ["A", "B", "C", "D", "E"]
         self.listopt2 = ["A"]
-
+
+    def tearDown(self):
+        self.config._drop()
+
     def test_geteval(self):
         """Test geteval returns correct object"""
         self.assertIsInstance(self.config.geteval('Evaluate', 'Option'), dict)
@@ -56,7 +59,7 @@ def test_geteval(self):
 class TestOldStyleConfig(unittest.TestCase):
     def setUp(self):
         self.configFile = pjoin(unittest_dir, 'test_data', 'test_config.ini')
-        
+
     def test_cnfReadIniValue(self):
         self.assertEqual(config.cnfGetIniValue(self.configFile, 'Integer', 'Option1'), 1)
         self.assertEqual(config.cnfGetIniValue(self.configFile, 'Integer', 'Option2'), 10)
@@ -69,7 +72,6 @@ def test_cnfReadIniValue(self):
         self.assertEqual(config.cnfGetIniValue(self.configFile, 'String', 'Option'), 'randomstring')
         self.assertEqual(config.cnfGetIniValue(self.configFile, 'Evaluate', 'Option'), {'x':1.0,'y':0.5})
 
-
     def test_returnDefault(self):
         self.assertEqual(config.cnfGetIniValue(self.configFile, 'Integer', 'Option3', 1), 1)
         self.assertEqual(config.cnfGetIniValue(self.configFile, 'String', 'Option2', 'otherstring'), 'otherstring')