Postgresql – How can calling a 3gb postgres table take up considerably more space than the table itself

I am making a data pipeline using python and am pulling a 3gb table from our RDS instance using psycopg2. Im currently testing this locally, and whenever I try this my Ram says my python instance is taking up 27gb which is not possible since I only have 8gb of ram.

Im not sure if this is relevant bythe pipeline takes the table and uses asyncio to asynchronously do post requests to the destination.

def query_database(
    query: str,
    query_args: str = None,
    dbname: str = os.environ.get('DBNAME'),
    user: str = os.environ.get('DBUSER'),
    password: str = os.environ.get('DBPASSWORD'),
    host: str = os.environ.get('LOCAL_BIND_ADDRESS'),
    port: int = int(os.environ.get('LOCAL_BIND_PORT'))
):
    with psycopg2.connect(
            dbname=dbname,
            user=user,
            password=password,
            host=host,
            port=port
        ) as conn:
        with conn.cursor() as cur:
            # Execute a query
            args = [query, query_args] if query_args else [query]
            cur.execute(*args)
            # Check if query returned rows and get them
            if cur.description:
                records = cur.fetchall()
                columns = [desc[0] for desc in cur.description]
                return pd.DataFrame(data=records, columns=columns)


query = sql.SQL("""SELECT * from table""")
query_database