add default extension for save_json

khandy/utils_file_io.py

@@ -34,6 +34,8 @@ def load_json(filename, encoding='utf-8'):
 
 
 def save_json(filename, data, encoding='utf-8', sort_keys=False):
+    if not filename.endswith('.json'):
+        filename = filename + '.json'
     with open(filename, 'w', encoding=encoding) as f:
         json.dump(data, f, indent=4, separators=(',',': '),
                   ensure_ascii=False, sort_keys=sort_keys)