Python Posts

I have create a google code project for my Python netstring module.

So what is a netstring? A netstring is a way of encoding strings of data in a file or network stream. The classic way of doing this is to terminate the string with a special character, such as carriage return, line-feed or a null byte. But this means that when reading the encoded data you have to check every character in the stream to see if it is the terminator character -- which can be inefficient. It also makes it impossible to encode a string that contains the terminator character, because it will be incorrectly interpreted as the end of the string. Netstrings solve both these problems by encoding the size of the string up-front. continue reading…

Just read an interesting blog post about comparing Python and Haskell code to calculate the Fibonacci sequence. I wrote a faster version, just for the hell of it. I realise that it is not a fair comparison any more, and doesn't prove anything, but it does demonstrate a useful optimization technique. Here's the code...

When I run it on my machine, it claims to take 0.00000 seconds. Damn, thats fast!

My employer has placed a number of bounties for wxPython features. Pays cash!

I got a bad review of my book on Amazon.com. I wanted to post a comment to address his points, but Amazon told me that I must have purchased an item to post -- which I have (many times)! So I thought I would post my comment here (below).

I'm the author of Beginning Game Development with Python and Pygame. Let me take a moment to comment on your scathing review.

1) As the title of the book indicates, the book is intended for beginners. As such there is an introduction to Python in the first two chapters. A total of 30 pages out of approximately 300. I don't think this is unreasonable. continue reading…

I've added the ability to becontrary for users to add their own debates. The debate regarding Python templates was quite successful so I hope Pythonistas will take advantage of this new feature to discuss Python-related topics. There's no restrictions on topics though, so feel free to create a debate on any topic. I think it is a great way of gathering opinions.

I've noticed that links in becontrary.com that have have a fragment (i.e. something after a #) don't always go to the exact location of the named anchor. I figured this was a Firefox bug originally, but I see the same thing in other browsers. I believe I have figured it out though. The browser changes the scroll position after the html is read, but before the stylesheets have been read. Once the browser has the CSS information the page updates, but because the CSS contains the dimensions of some elements, the named anchor changes position -- but the scroll position doesn't update accordingly. At least thats my working theory.  The only solution I can think of for this is to make all my style sheets inline -- but that would mean I wouldn't have the cache-related benefits of having them external. I can't be the first developer to be irritated by this. Can anyone offer a solution?

The site was also the subject of a bit of vandalism. One user was repeatedly posting page after page of garbage text. Another user posted an argument where he professed his desire to perform fellatio (in slightly different terminology), which was kind of off-topic. So I hurriedly had to implement some anti-jerk technology to prevent flooding. I also had to add the ability to the admin page to completely wipe a users arguments / comments, something which I had naively thought I wouldn't need. The truth is though, that this type of site is vulnerable to vandalism, and if somebody wanted to make a nuisance of themselves then it wouldn't be difficult. All I could do is retroactively clean up the mess. I've had no problems with spam so far, because I implemented a number of anti-spam measures that using javascript to present different content to users than would be seen by a bot. It would be quite easy circumvent, but I can change the technique if spam becomes an issue -- or implement a captcha solution. continue reading…

There are a number of (very good) templating systems and languages available for Python. They fall in to one of two camps; either they are XML based, like Genshi, or they are text based, like Mako. Most programmers favour one or the other, but there is far from a consensus over which is better.

I'd like to use this debate to gather reasons for using one over the other in the context of web development. I suspect there will be no clear winner, but it should serve as a useful resource for those faced with the decision!

Here's the caching decorator I mentioned in my previous blog entry about optimizing the front page of becontrary.com. It is pretty simple to use, you supply the same parameters to it as timedelata. So @timed_cache(minutes=30) would cache the result for half an hour. It is thread safe, so you can happily use it in the context of a web application, such as Turbogears. For many things it is a magical one-line speed-up, but there are some issues to be aware of. You can't use it to cache anything where the return value is context sensitive, such as SQLObject class instances -- because they are tied to a database context that wont exist at the second call. If you do want to cache such objects, then you should copy the information you need to a dictionary. Genshi templates make the difference completely transparent, so it is not much of a problem. Another issue is that parameters must be immutable, because they are used as keys in a dictionary.