I am using psycopg2 & sqlalchemy to connect to a database and extract information from a table as follows:

def db_connection():
        eng = db.create_engine('my_URI')
        conn = eng.connect()
        return eng, conn

def table_conn():
    engine, connection = db_connection()
    metadata = db.MetaData()

    admin_table = db.Table(
    return engine, connection, admin_table

def get_table_data(user_id):
    _, connection, table_data = table_conn()

    # first filter using user_id and sort the data by datetime column
    query = db.select([table_data]).where(
        table_data.columns.user_id == user_id,
    result = connection.execute(query).fetchall()

    # 5th element is time
    # filtering the data to find data that has been saved at the same time
    # making it the latest data
    time = result[0][5]
    time_filtering_query = db.select([table_data]).where(
        table_data.columns.created_at == time
    time_result = connection.execute(time_filtering_query).fetchall()
    return time_result

The functions: db_connection() & table_conn() are connecting to the database and the table respectively.

In the get_table_data function, I am doing the following:

  1. Use the user_id to filter the table
  2. Order the table in desc order on the created_at column (which is the 5th column of the table)
  3. Extract the first created_at value (which is result[0][5] in the code above)
  4. And use this extracted value to filter the table again

In the code, I am hardcoding the column index in the result[0][5] part. Is there a way the above code can be modified to avoid hardcoding of the values and filter the values, if possible, based on the column names or in any other neater way?


1 Answer 1


You should avoid doing [0] after your query. Instead, add a .limit(1) at the end of your select.

SQA supports named column references on individual result tuples. So in addition to supporting [5], which is (as you've identified) a bad idea - it should just support .time assuming that's what your column name is. However, even better is - rather than selecting the entire table_data - simply select only the column you want.

  • \$\begingroup\$ Thanks a lot for the clue. This was really helpful \$\endgroup\$
    – Junkrat
    May 3, 2021 at 15:42

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