python2 与 python3 raise 语句

Question

在 flask 文档中有一个钩子(Hook)函数的示例，当没有找到 flask 定义的 url 端点时，它允许通过调用为 url_for 函数添加自定义行为。如果也没有匹配的用户定义的 url 端点，程序员可以添加自定义端点或重新引发异常(使用原始上下文)。

def external_url_handler(error, endpoint, values):
    "Looks up an external URL when `url_for` cannot build a URL."
    # This is an example of hooking the build_error_handler.
    # Here, lookup_url is some utility function you've built
    # which looks up the endpoint in some external URL registry.
    url = lookup_url(endpoint, **values)
    if url is None:
        # External lookup did not have a URL.
        # Re-raise the BuildError, in context of original traceback.
        exc_type, exc_value, tb = sys.exc_info()
        if exc_value is error:
            raise exc_type, exc_value, tb
        else:
            raise error
    # url_for will use this result, instead of raising BuildError.
    return url

app.url_build_error_handlers.append(external_url_handler)

此代码片段似乎是 python2 代码，但由于 raise exc_type, exc_value, tb 行而无法用于 python3。 python2和 python3文档列出了 raise 语句的不同参数。

将此代码段转换为 python3 的正确方法是什么？

Answer 1

这在 the raise statement 的文档中指定:

You can create an exception and set your own traceback in one step using the with_traceback() exception method (which returns the same exception instance, with its traceback set to its argument), like so:

raise Exception("foo occurred").with_traceback(tracebackobj)

因此，在您的情况下，这将是:

raise exc_type(exc_value).with_traceback(tb)