Demo of attrgetter to process a previously defined list of namedtuple called metro_data

Attrgetter.py

>>> from collections import namedtuple
>>> 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') # 
>>>
>>> for city in sorted(metro_areas, key=attrgetter('coord.lat')): # 
... print(name_lat(city)) # 
...