[Python-Dev] Re: "groupby" iterator

[Raymond Hettinger]

[Thomas Heller]
> > Looking at parts of my codebase nearly all uses of lambda are
> > 'lambda self: self.someattr'.

Yes, they are everywhere.
Getting rid of those lambdas was part of the attraction for
attrgetter().


> But, at least for attrgetter, I am slightly unhappy with the outcome,
> because the attribute name is now expressed as a string literal rather
> than using attribute notation.  This makes it harder to write
> automated tools that check or optimize code.  (For itemgetter it
> doesn't really matter, since the index is a literal either way.)
> 
> So, while I'm not particularly keen on lambda, I'm not that keen on
> attrgetter either.  But what could be better?  

I don't know if you like this, but there is a way to change the
interface to attrgetter() so that the dot notation can be used 
instead of a string.  It produces the same result and is neater,
but I find it somewhat harder to explain:



import operator

class NewAttrGetter(object):
    def __getattribute__(self, name):
        return operator.attrgetter(name)

newattrgetter = NewAttrGetter()

class A:
    pass
a = A()
a.score = 10

getscore = operator.attrgetter('score')
print getscore(a)

getscore = newattrgetter.score
print getscore(a)



new-style-classes-rock-ly yours,



Raymond Hettinger