Thursday, November 27, 2008

Labelled Reduction as A Good Thing

One small thing (of the many) in Python 2.6 I like (and have waited for since it appeared as a recipe), is collections.namedtuple. It is very useful in itself, but the fact that the stdlib has been adapted to use it throughout is quite nice. Consider the following code:
from urlparse import urlparse
print urlparse(
If run with Python 2.5, you get this tuple:
('http', 'localhost:8080', '/doc/something',
'en', 'rev=1', '')
, whereas in 2.6 it is a namedtuple:
scheme='http', netloc='localhost:8080',
params='en', query='rev=1', fragment='')
The last one is unpackable just like a regular tuple, but you can access the parts as attributes as well. This little "data struct" is quite handy, since I don't like to access tuples by index, but quite often pass them around and only access some piece of them at a time.

(With these you don't need to create full-fledged classes for every kind of instrumental data. (Sometimes coupling data and functionality in a single paradigm may be a coarse hammer, treating nails and iron chips alike..) Nor resort to the use of dictionaries where you really want a "restricted value lens", if you will.. But this is another rant altogether.)

Of course, there's lots more to enjoy in 2.6 (the enhanced property for decorator use, ABC:s, json, 2to3 etc).

On a related note, do check out Swaroop C H:s excellent and free books on Python (2.x + 3.0(!)): A Byte of Python. And if you're into Vim (you should be, IMHO) his new A Byte of Vim.

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