Deciphering
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Push F9 To Continue

Wed 22 February 2006

F9 is the default keybinding for "run the unit tests for the current file" when using the Twisted Emacs bindings.

As her Windows/Divmod tutorial indicates, Ying is getting started with coding using Twisted again. This is the third time that she's gotten started with it - tries #1 and #2 involved Woven and Nevow, respectively. I was cringing as she started to get her development environment set up, because those previous attempts were shockingly painful. Every step of the way was a challenge - version skew. Path problems. Obscure deprecation warnings. Un-debuggable template interactions. Undocumented assumptions. DOCTYPE declarations.

This time she's got a bit more of a domain-model problem to attack. It was staggering to me how different it was. While getting started with a web-based development project with Twisted was painful, and it wasn't necessarily clear how to proceed, getting started with a domain model was trivial. With a 4-line unit test template, she was productive within 5 minutes. Of course, having yours truly in the room (and emotionally dependent upon you) when you start to work on a Twisted program helps, but I have been largely uninvolved - as opposed to previous attempts where she would ask a question every 5 minutes and I would start the answer with, "You have to understand the history of the multiple projects involved here..." or "There are some unresolved issues...", now she asks a question once per day or so, and the answers are short, direct sentences like "use twisted.web.client.getPage" or "return a Deferred from your test method".

I have long despaired of Twisted development being easy to newcomers, and the community (both friendly and hostile to Twisted) reinforces this assumption. "Asynchronous programming is too hard", "learning Twisted is a serious investment of time", "there's so much you have to know to get started", etc. However, I've now seen that it can be easy. We just need more tutorials that blitz through the introductory steps on a particular platform without explaining anything, and get straight to coding something.

For example, if I had written the tutorial that Ying posted to her blog, I probably would have explained each step, so as to give users maximal flexibility in their setup. "Make a folder to hold your projects. We'll call this the 'combinator container' folder from now on. You can place this anywhere on your sys.path. Now, make a folder /path/to/combinator-container/Divmod ..." Ying chose a much more direct route. Nobody really cares what the folder is named, they just want things to work. "Make a folder C:\Projects. Now make a folder inside that called Divmod. Then run 'svn co ...'"

Once you have gotten to the point where you are hitting F9 every five minutes, watching your code run, and fixing problems, you don't really care that you don't know how to put C:\Projects at H:\Documents and Settings\%USER%\My Documents\Programming\MyNiftyProject\Infrastructure. You don't care that you had to run svn command lines rather than installers. You certainly don't care why version 0.9.8a of OpenSSL is required or where ZopeInterface was installed.

That last step - where you just push a button, rather than starting up a terminal and typing a command line - is an important one. It makes the experience feel complete, and it removes a point in the development process (that happens every 5 minutes or so) where a new Twisted user thinks, "this is a pain in the ass, these tools are terrible".

twisted-dev.el is the best-kept secret of Twisted developers. It needs to be more front-and-center. We should eschew the bits that never really worked, and are no longer maintained, i.e. the PB/Emacs integration, and include the core one-button-unit-test functionality with Twisted itself.