Clean up format strings

It is better to format the string all at once instead of using
both formatting and concatenate.

chatterbot/corpus.py

@@ -24,8 +24,9 @@ def get_file_path(dotted_path, extension='json'):
 
     corpus_path = os.path.join(*parts)
 
-    if os.path.exists(corpus_path + '.{}'.format(extension)):
-        corpus_path += '.{}'.format(extension)
+    path_with_extension = '{}.{}'.format(corpus_path, extension)
+    if os.path.exists(path_with_extension):
+        corpus_path = path_with_extension
 
     return corpus_path
 

chatterbot/logic/mathematical_evaluation.py

@@ -55,7 +55,8 @@ def process(self, statement, additional_response_selection_parameters=None):
         response = Statement(text=expression)
 
         try:
-            response.text += ' = ' + str(
+            response.text = '{} = {}'.format(
+                response.text,
                 mathparse.parse(expression, language=self.language.ISO_639.upper())
             )