Operator Module
The operator module provides functions equivalents for dozens of operators so you don’t have to code trivial function like lambda a, b: a*b.
operator.mul
Multiplication operator.
mul_operator.py
>>> def factorial(n):
... return reduce(lambda a, b: a*b, range(1, n+1))
>>>
>>> from functools import reduce
>>> from operator import mul
>>> def factorial(n):
... return reduce(mul, range(1, n+1))
operator.itemgetter and operator.attrgetter
itemgetter and attrgetter are factories that pick items from sequences or read attributes from object.
itemgetter uses the [] operator, it supports not only sequences but also mappings and any class that implements __getitem__;
itemgetter.py
>>> metro_data = [
... ('Delhi NCR', 'IN', 21.935, (28.613889, 77.208889)),
... ('Mexico City', 'MX', 20.142, (19.433333, -99.133333)),
... ('São Paulo', 'BR', 19.649, (-23.547778, -46.635833)),
... ]
>>> from operator import itemgetter
>>> for city in sorted(metro_data, key=itemgetter(1)):
... print(city)
>>> cc_name = itemgetter(1, 0)
>>> for city in metro_data:
... print(cc_name(city))
('São Paulo', 'BR', 19.649, (-23.547778, -46.635833))
('Delhi NCR', 'IN', 21.935, (28.613889, 77.208889))
('Mexico City', 'MX', 20.142, (19.433333, -99.133333))
('IN', 'Delhi NCR')
('MX', 'Mexico City')
('BR', 'São Paulo')
attrgetter creates functions to extract object attributes by name. attrgetter can navigate through nested objects that contains a .(dot), to retrieve the attribute.
attrgetter.py
>>> metro_data = [
... ('Delhi NCR', 'IN', 21.935, (28.613889, 77.208889)),
... ('Mexico City', 'MX', 20.142, (19.433333, -99.133333)),
... ('São Paulo', 'BR', 19.649, (-23.547778, -46.635833)),
... ]
... ...
>>> 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]
>>> print(metro_areas[0])
>>> from operator import attrgetter
>>> name_lat = attrgetter('name', 'coord.lat')
>>> for city in sorted(metro_areas, key=attrgetter('coord.lat')):
... print(name_lat(city))
Metropolis(name='Delhi NCR', cc='IN', pop=21.935, coord=LatLon(lat=28.613889, lon=77.208889))
('São Paulo', -23.547778)
('Mexico City', 19.433333)
('Delhi NCR', 28.613889)
operator.methodcaller
Creates a function that calls a method by name on the object given as argument.
lambda.py
>>> from operator import methodcaller
>>> s = 'The time has come'
>>> upcase = methodcaller('upper')
>>> print(upcase(s))
>>> hyphenate = methodcaller('replace', ' ', '-')
>>> print(hyphenate(s))
THE TIME HAS COME
The-time-has-come