関連ワード:  python append to list if does not exist    python add to list if does not exist    python add value to list if it does not exist    python add element to list if it does not exist    python append to list if not present    python append to list create if not exist    python add to list if it doesn't exist    python add to list if not present    python add to list only if not exist    python add dict to list if not exists  
結果 : python append to list if does not exist