Update elo.py

elo.py

@@ -23,7 +23,7 @@ def update_elo_ratings(ratings_dataset, winner, loser, k_factor=32):
     for player in [winner, loser]:
         if player not in ratings_df['bot_name'].values:
             new_player = {'bot_name': player, 'elo_rating': 1200}
-            ratings_df = ratings_df.append(new_player, ignore_index=True)
+            ratings_df = pd.concat([ratings_df,pd.DataFrame([new_player])],ignore_index=True)
 
     # Extract old ratings
     winner_old_rating = ratings_df.loc[ratings_df['bot_name'] == winner, 'elo_rating'].iloc[0]