Defaulting to default value in case no variable usage exists for vari…

…able

optimizely/project_config.py

@@ -424,7 +424,7 @@ def get_variable_value_for_variation(self, variable, variation):
       variation: The Variation for which we are getting the variable value.
 
     Returns:
-      The type-casted variable value or None if any of the inputs are invalid.
+      The variable value or None if any of the inputs are invalid.
     """
 
     if not variable or not variation:
@@ -438,9 +438,10 @@ def get_variable_value_for_variation(self, variable, variation):
     variable_usages = self.variation_variable_usage_map[variation.id]
 
     # Find usage in given variation
-    variable_usage = variable_usages[variable.id]
+    variable_usage = variable_usages.get(variable.id)
 
-    return variable_usage.value
+    # Return default value in case there is no variable usage for the variable.
+    return variable_usage.value if variable_usage else variable.defaultValue
 
   def get_variable_for_feature(self, feature_key, variable_key):
     """ Get the variable with the given variable key for the given feature.

tests/test_config.py

@@ -1226,6 +1226,17 @@ def test_get_variable_value_for_variation__no_variables_for_variation(self):
     is_working_variable = project_config.get_variable_for_feature('test_feature_in_experiment', 'is_working')
     self.assertIsNone(project_config.get_variable_value_for_variation(is_working_variable, variation))
 
+  def test_get_variable_value_for_variation__no_usage_of_variable(self):
+    """ Test that a variable with no usage will return default value for variable. """
+
+    opt_obj = optimizely.Optimizely(json.dumps(self.config_dict_with_features))
+    project_config = opt_obj.config
+
+    variation = project_config.get_variation_from_id('test_experiment', '111128')
+    variable_without_usage_variable = project_config.get_variable_for_feature('test_feature_in_experiment',
+                                                                              'variable_without_usage')
+    self.assertEqual('45', project_config.get_variable_value_for_variation(variable_without_usage_variable, variation))
+
   def test_get_variable_for_feature__returns_valid_variable(self):
     """ Test that the feature variable is returned. """