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Showing posts from June, 2005

Python: Generator Expressions

In one of his talks at PyCon, Alex Martelli said that if you have complicated loop logic, throw it into a generator so that you never have to duplicate it. In the old days, it was common to duplicate loop logic. I like this rule, and I have seen it improve my code. Just in case you haven't seen the syntax yet, it's: >>> def generate(): ... yield 1 ... yield 79 ... yield 26 ... for i in range(0, 10): ... yield i ... >>> for i in generate(): ... print i, ... 1 79 26 0 1 2 3 4 5 6 7 8 9 In Python 2.4, generator expressions were added. When I saw these, I figured, "Well, yeah, that's pretty natural." It took me a while to realize that just as list comprehensions were taken from Haskell, generator expressions are lazy lists from Haskell. Again, here's an example: >>> import itertools >>> import random >>> >>> numbers = (random.random() for i in itertools.repeat(0)) >>>

Python: HTMLTemplate

Paul Abrams suggested to me the idea of having 100% pure HTML, and then using some DOM on the server side to splice chunks of HTML together. After talking about it for about two hours, I became excited about the idea, and I wondered if it would be pleasant in practice in contrast to, say, Cheetah . At the very least, it would be an interesting alternative. It turns out that HTMLTemplate is one such system. I asked the Python web-sig about it, as well as a few other people. Tung Wai Yip said that he really liked HTMLTemplate. I figured my buddy, Donovan Preston, of Nevow fame would like it because he's a fan of getting away from the whole "big chunk of HTML in an amorphous string" idea. Ian Bicking had the following comment, which I feel was very perceptive: If there's no code then it's not a presentation layer. It's an HTML layer, nothing more, just dumb data. Presentation requires logic. Ksenia Marasanova, the newest member added to the Aquarium