Programming Language :: Python :: Understanding Twisted Deferred

最新推荐文章于 2025-08-07 15:08:44 发布

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本文深入探讨了Deferred这一Python对象类型，它专用于编码执行顺序，以回调形式分离并独立于普通Python源代码顺序。通过实例说明，文章解释了如何使用Deferred在异步操作中实现特定的执行顺序，包括成功异步操作后的操作、错误处理、并发操作管理等关键功能。

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What is Deferred

Deferred is a type of object designed to do one thing only:
encode the execution order as callback-based and separately from the normal order of the python source codes.

What does and not does

It does not deal with threads, parallelism, signals or subprocesses.
It does not no know anything about an event loop, green lets or scheduling.
All it knows is what order to do things that we explicitly tell it the order we want.

Thus, instead of writing:

door.open();    
pad.launch();

We write:

d = door.open();   
d.addCallBack(pad.launch);

Summary

Do something after an asynchronous operation completes successfully
Use the result of a successful asynchronous operation
Catch errors in asynchronous operations
Do one thing if an operation succeeds, and a different thing if it fails
Do something after an error has been handled successfully
Wrap multiple asynchronous operations with one error handler
Do something after an asynchronous operation, regardless of whether it succeeded or failed
Write code without callbacks using inline Callbacks