Python’s with statement can be a very elegant alternative to long try/except/finally clauses. It offers a standard protocol that classes can implement to properly clean up state. The best example for it’s value is file reading. A good implementation would have to look like this traditionally: f = open('/tmp/myfile', 'r') try: content = f.read() finally: f.close() The with statement shortens this to the following code: with open('/tmp/myfile', 'r') as f: content = f.read() Behind the scenes it wraps the finally statement around this and makes sure that the file gets closed upon leaving the with block. ...

As most programmers, I’ve been trained with the getter/setter idiom. It allows a programmer in any object-oriented programming language to create a class interface which makes sure that only valid data is written. An example of a class with getter/setter in Python: class Person1(object): def __init__(self): self._age = None def get_age(self): return self._age def set_age(self, age): self._age = age We just wrote two methods - four lines - only to be able to modify and access some data. And we have to do that for every property. This is such a common idiom, that IDEs even have wizards for that. ...

Starting with Python 2.6 there is a new format function to do string formatting. I’ve always been a bit overwhelmed by the official Format String Syntax documentation so I’ll try to present it to you with more examples. Python so far had the ‘%’ operator. It’s been deprecated with Python 2.6 and removed from Python 3. Instead string has a new format method. >>> "This is an %s-style formatting" % "old" 'This is an old-style formatting' >>> "This is a {0}-style formatting".format("new") 'This is an new-style formatting' Formatting options go after a colon, for example the width specifications together with alignment options which are mostly useful for tabular representations. Let’s print the following table as an exercise: ...

With the Pot: String formatting I’m starting a series on my blog: Python on the toilet. I’ll try to write short and dense introductions for Python features or packages. Each introduction should fit on a A4 paper. So if you want to, you could print it out and hang on your toilet doors. I’m not entirely sure yet what I’ll cover, but we’ll see what comes up. If you have topic proposals shoot me a mail. ...

Yesterday evening we had the very first swiss.py. Thanks to Uche Mennel for doing a very interesting presentation about Traits. I was really happy about the number and diversity of people who showed up. The next swiss.py will take place on March 31 with Florian Bösch doing a presentation related to OpenGL programming in Python. Details and location will follow.

Code reviews are an important instrument to keep the code quality high. There are all kinds of schools on how to do this. For the local.ch frontend we made pre-checkin code reviews mandatory for a few core components including the Okapi framework. For all other components and applications, developers can request code reviews if they wish. For this to work without the developers being annoyed with the process, code reviews must be super-easy. When first starting with code reviews at local.ch I tested a ton of tools. But none of them quite fit our workflow. In the end we went for LodgeIt. LodgeIt is “only” a pastebin application. But it works amazingly well for code reviews because it has some advanced functionality such as replying and then diffing the reply to the original. ...

I currently work at a startup which we’re financing from our own pockets. So I’m always looking for a way to save some money. And I found a way to save almost 1000 Swiss Francs on my public transport bills this year. The GA is the train flat-rate as sold by the Swiss train company SBB. There is complicated tariff jungle for how much it costs. This is how I bought the GA so far: ...

Chris Siebenmann motivated me to finally do something about the situation of my web site passwords. So I needed some nice password generation process. I looked at 1password but didn’t find it terribly attractive. Instead I’m using the OSX keychain. For generating passwords I use the excellent apg. And since today this shell function: clippass() { apg -M SNCL -m 15 -n 1 | pbcopy pbpaste } This creates a long and safe password, pastes it to the clipboard using pbcopy and then shows it on the command line by pasting it again from the clipboard using pbpaste. ...

Intro Probably my favourite project at local.ch was news.local.ch. That’s a site which crawls Swiss newspapers for news and classifies them by town. It only shows news which can be associated with any Swiss town. This leads to a good news collection even for very small villages. In this post I’m going to outline the architecture and how we used Amazon’s web services to make building this a lot easier than it could have been. There will be a follow-up detailing how we used Python in this project. ...

I really love The Economist. It’s a must-read for me every week. Many weeks it’s the only news I read. But lately I’ve been wanting to read it in the train on my iPhone, especially as the online version is up one night before I got my print edition. But the online version of The Economist is just too fat. Tons of Javascript and ads which make it a slow experience. The Tabulate bookmarklet helped a little to ease the pain. But not much. ...