python-3.x - 未提取SQLAlchemy OperationalError

Question

因为我们需要使用不同的URL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，try/except子句未提取引发的OperationalError。为什么未提取此错误？

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仅创建实例，但不建立连接。
您需要连接到数据库以验证连接是否有效。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"))