httpclient import HTTPClient def synchronous_fetch(url): http_client = HTTPClient() response = http_client.fetch(url) return response.body And here is the same function rewritten asynchronously as a native coroutine: AsyncHTTPClient async def asynchronous_fetch(url): http_client = AsyncHTTPClient() response = await http_client.fetch(url) return response.body Or for compatibility with older versions of Python, using the tornado coroutine def async_fetch_gen(url): http_client = AsyncHTTPClient() response = yield http_client.fetch(url) raise gen.Return(response.body) Coroutines are a little magical, but what they do internally

main coroutine The Application object Subclassing RequestHandler Handling request input Overriding RequestHandler methods Error Handling Redirection Asynchronous handlers Templates and UI Configuring HTTPClient def synchronous_fetch(url): http_client = HTTPClient() response = http_client.fetch(url) return response.body And here is the same function rewritten asynchronously as a native def asynchronous_fetch(url): http_client = AsyncHTTPClient() response = await http_client.fetch(url) return response.body Or for compatibility with older versions of Python, using the tornado

Compiling error-handling v0.1.0 (file:///projects/error-handling) Finished `dev` profile [unoptimized + debuginfo] target(s) in 0.73s Running `target/debug/error-handling` thread 'main' panicked main 函数的返回类型是 () 而不是 Result。当编译这些代码，会得到如下错误信息： $ cargo run Compiling error-handling v0.1.0 (file:///projects/error-handling) error[E0277]: the `?` operator can only be used in a function that returns information about this error, try `rustc --explain E0277`. error: could not compile `error-handling` (bin "error-handling") due to 1 previous error 这个错误指出只能在返回 Result、Option 或者其它实现了 FromResidual 的类型的函数中使用