At 09:57 PM 11/30/03 +0100, Alex Martelli wrote:
students.sort(key=attrgetter('grade')) # key=lambda r:r.grade students.sort(key=itemgetter(2)) # key=lambda r:[2] students.sort(key=itemgetter('grade')) # key=lambda r:r['grade']
I concur: "overloading" extract to mean (the equivalent of) either getattr or getitem depending on the argument type doesn't look good, besides making it unusable to extract some items from dicts.
Since these functions or types are going to be in operator, I think we can afford to "spend" two names to distinguish functionality (even though attgetter and itemgetter look nowhere as neat as extract -- I don't have better suggestions offhand).
How about: extract(attr='grade') extract(item=2) extract(method='foo') # returns the result of calling 'ob.foo()' And following the pattern of Zope's old "query" package: extract(extract(attr='foo'), attr='bar') # extracts ob.foo.bar extract(extract(item=10), method='spam') # extracts ob[10].spam() i.e., the first (optional) positional argument to extract is a function that's called on the outer extract's argument, and the return value is then used to perform the main extract operation on. IIRC, the Zope query package used __getitem__ instead of __call__ on its instances as a speed hack, but I don't think we should follow that example. :)