diff --git a/underthesea/utils/col_external_dictionary.py b/underthesea/utils/col_external_dictionary.py
index b9565301..4d82f0dc 100644
--- a/underthesea/utils/col_external_dictionary.py
+++ b/underthesea/utils/col_external_dictionary.py
@@ -26,10 +26,7 @@ def __init__(self, word, senses=[]):
         self.senses = senses
 
     def __str__(self):
-        content = self.word + " "
-        for sense in self.senses:
-            content += sense.tag + ","
-        return content
+        return self.word + " " + ",".join([sense.tag for sense in self.senses]) + ","
 
     def add_sense(self, sense):
         self.senses.append(sense)