Write string not int

model.py

@@ -51,7 +51,7 @@ def put_timestamp_stored(this_timestamp):
     :return:
     """
     with open('timestamp.txt', 'w') as f:
-        f.write(this_timestamp)
+        f.write("{}".format(this_timestamp))
 
 
 def get_data(stock_id, this_timestamp):