On Wed, Apr 2, 2014 at 10:15 PM, Rustom Mody <rustompm...@gmail.com> wrote: > On Thursday, April 3, 2014 8:11:33 AM UTC+5:30, Rustom Mody wrote: >> On Wednesday, April 2, 2014 11:28:16 PM UTC+5:30, Roy Smith wrote: >> > I have a big hairy data structure which is a tree of nested dicts. I have >> > a sequence of strings which represents a path through the tree. Different >> > leaves in the tree will be at different depths (which range from 1 to >> > about 4 or 5 at most). I want to get the value stored at that path. >> > Thus, if > >> > keys = ['foo', 'bar', 'baz'] > >> > I want to retrieve tree['foo']['bar']['baz']. > >> > Is there some idiomatic, non-cryptic way to write that as a one-liner? > >> > I'm using Python 2.7. > >> What you are asking for is probably: > >> >>> reduce((lambda tr, att: tr[att]), ['a','b','c'], nested) >> 'Hiii!!' > > Shorter version: > >>>> reduce(dict.get, ['a','b','c'], nested) > 'Hiii!!'
That breaks if the dicts are ever replaced with an alternate mapping implementation (or a dict subclass that overrides the get method), and incorrectly returns None instead of raising KeyError if the last key in the sequence does not exist (and if any of the other keys don't exist, you'll get a TypeError instead of a KeyError). This is more robust: import operator reduce(operator.getitem, ['a', 'b', 'c'], nested) -- https://mail.python.org/mailman/listinfo/python-list
