Succinct Python
Apropos of nothing…
Having passed beyond the macho need to write obscure code, I’m not fond of
coding constructs that make me scratch my head. But I found this yesterday
in the Python Cookbook (2nd Ed.) p705.
from itertools import izip
def chop(iterable, length=2):
return izip(*(iter(iterable),) * length)
It took me a few minutes to figure out exactly how it does what it does. Talk about succinct. It’s probably very efficient too.
One thing I really don’t like, and which is a chronic problem in perl, is reusing symbols for multiple purposes. In the above, the first * is expanding a list into multiple arguments to izip, while the second * is multiplying (a list). Thankfully, Python is almost completely free of that problem.
There’s also the reliance on the precedence of the latter being higher than the former. I actually do approve of that – I think if you’re going to program seriously with a language you should at least have a fair grip on the precedence of its operators. Not doing so means your code winds up littered with unneeded parens. While it’s nice to be explicit, and “explicit is better than implicit” is one of the Python guidelines, the rules of precedence are already explicit. To put in parens where they’re not needed can make your code less easily to follow at a glance for someone who does know the language. That’s because when reading such code, you look at it more carefully, figuring that those parens must be there for some good reason, because the person who put them in obviously didn’t want the default precedence to apply. When you realize that they’re unnecessary, it’s frustrating and a worry, because you’ve just wasted time and you realize you’re reading the code of someone who either enjoys putting in unneeded syntax or doesn’t know the language well. And who wants to deal with either of those?
Anyway, even if you immediately know what the two * symbols are doing and about the precedence, it’s still nice to think all the way through the above. How/why does it work? When do the iterators stop? Who catches and deals with StopIteration, what happens if the length of iterable is not zero mod length?
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