4fmy-packages-for-functional-programming-in-python.md

Packages For Functional Programming in Python

#python #programming #functional #datamodel

• operator: sum, mul
• functools: reduce
• itemgetter: Catch one item from the sequence [[4dyw-python-sequences]]
  • Need to have __getitem__ implemented

>>> 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)),
...     ('São Paulo', 'BR', 19.649, (-23.547778, -46.635833)),
... ]
>>> cc_name = itemgetter(1, 0)
>>> for city in metro_data:
...     print(cc_name(city))
('JP', 'Tokyo')
('IN', 'Delhi NCR')
('MX', 'Mexico City')
('US', 'New York-Newark')
('BR', 'São Paulo')

• attrgetter: Catch one attribute from class

>>> from collections import namedtuple
>>> LatLon = namedtuple('LatLon', 'lat lon')
>>> Metropolis = namedtuple('Metropolis', 'name cc pop coord')
>>> metro_areas = [Metropolis(name, cc, pop, LatLon(lat, lon))
...     for name, cc, pop, (lat, lon) in metro_data]
>>> metro_areas[0]
Metropolis(name='Tokyo', cc='JP', pop=36.933, coord=LatLon(lat=35.689722,
lon=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))
...
('São Paulo', -23.547778)
('Mexico City', 19.433333)
('Delhi NCR', 28.613889)
('Tokyo', 35.689722)
('New York-Newark', 40.808611)

References

• Ramalho, 2022, p243-247