SQLAlchemy OperationalError未取

Question

因为我们需要使用不同的urls来访问数据库以供内部和外部使用，所以我实现了以下代码。问题是，引发的OperationalError不是由try/ not子句获取的。为什么不取这个错误？

try:
    return create_engine('postgresql://{user}:{password}@{host}:{port}/{dbname}'.format(
            dbname="db_name",
            user="username",
            host="internal_url.com",
            port=1234,
            password="PassWord"))
except exc.OperationalError:
    return create_engine('postgresql://{user}:{password}@{host}:{port}/{dbname}'.format(
            dbname="db_name",
            user="username",
            host="external_url.com",
            port=1234,
            password="PassWord"))

Answer 1

create_engine只创建实例，但不建立连接。您需要连接到数据库，以验证连接是否有效。就像这样

try:
    engine = create_engine('postgresql://{user}:{password}@{host}:{port}/{dbname}'.format(
            dbname="db_name",
            user="username",
            host="internal_url.com",
            port=1234,
            password="PassWord"))
    engine.connect()
    return engine
except sqlalchemy.exc.OperationalError:
    return create_engine('postgresql://{user}:{password}@{host}:{port}/{dbname}'.format(
            dbname="db_name",
            user="username",
            host="external_url.com",
            port=1234,
            password="PassWord"))