import psycopg2
from psycopg2 import pool
class PgDB:
    """Класс для работы с БД"""
    def __init__(self):
        connection_string = "...тут строка подключения..."
        try:
            self.__pool = psycopg2.pool.ThreadedConnectionPool(1, 10, connection_string)
            self.__conn = self.__pool.getconn()
        except psycopg2.pool.PoolError as e:
            self.__pool = None
            self.__conn = None
            raise(e)
        except Exception as e:
            print(" Unknown error")
            raise(e)
    def __enter__(self):
        return self.__conn
    def __exit__(self, exc_type, exc_val, exc_tb):
        if exc_type is not None:
            self.__conn.rollback()
        try:
            self.__conn.commit()
        except Exception:
            self.__conn.rollback()
        finally:
            self.__conn.close()
    def execute(self, sqltext='select 1'):
        ps_cursor = self.__conn.cursor()
        ps_cursor.execute(sqltext)
        records = ps_cursor.fetchall()
        ps_cursor.close()
        self.__pool.putconn(self.__conn)
        return records

 print(PgDB().execute('select * from objects limit 10'))

 with PgDB() as db:
    a = db.execute('select * from objects limit 10')

 def __enter__(self):
        return self