"""

Return a callable object that fetches attr(by name) from its operand

* After f = attrgetter('name'), the call f(b) returns b.name.

* After f = attrgetter('name', 'date'), the call f(b) returns (b.name, b.date)

* After f = attrgetter('name.first', 'name.last'), the call f(b) returns (b.name.first, b.name.last)

If several attribute names given as arguments, it returns a tuple of values

If any argument name contains a.(dot), attrgetter navigates through nested objects to retrieve the attribute

>>> from collections import namedtuple

>>> metro_data = [

... ('Tokyo', 'JP', 36.933, (35.689722, 139.691667)),

... ('Delhi NCR', 'IN', 21.935, (28.613889, 77.208889)),

... ('Mexico City', 'MX', 20.142, (19.433333, -99.133333)),

... ('New York-Newark', 'US', 20.104, (40.808611, -74.020386)),

... ('Sao Paulo', 'BR', 19.649, (-23.547778, -46.635833))]

>>> LatLong = namedtuple('LatLong', 'lat long')

>>> Metropolis = namedtuple('Metropolis', 'name cc pop coord')

>>> metro_areas = [Metropolis(name, cc, pop, LatLong(lat, long))

... for name, cc, pop, (lat, long) in metro_data]

>>> metro_areas[0]

Metropolis(name='Tokyo', cc='JP', pop=36.933, coord=LatLong(lat=35.689722, long=139.691667))

>>> metro_areas[0].coord.lat

35.689722

>>> from operator import attrgetter

>>> name_lat = attrgetter('name', 'coord.lat') # define a attrgetter

>>> for city in sorted(metro_areas, key=attrgetter('coord.lat')):

... print(name_lat(city))

('Sao Paulo', -23.547778)

('Mexico City', 19.433333)

('Delhi NCR', 28.613889)

('Tokyo', 35.689722)

('New York-Newark', 40.808611)

"""

if __name__ == "__main__":

import doctest

doctest.testmod()