Reduce by key in python -


i'm trying think through efficient way in python.

suppose have list of tuples:

[('dog',12,2), ('cat',15,1), ('dog',11,1), ('cat',15,2), ('dog',10,3), ('cat',16,3)]

and suppose have function takes 2 of these tuples , combines them:

def my_reduce(obj1, obj2):     return (obj1[0],max(obj1[1],obj2[1]),min(obj1[2],obj2[2]))

how perform efficient reduce 'key' key here first value, final result like:

[('dog',12,1), ('cat',16,1)]

if want use my_reduce , reduce, can way. it's short, actually:

preparation:

from itertools import groupby operator import itemgetter  pets = [('dog',12,2), ('cat',15,1), ('dog',11,1), ('cat',15,2), ('dog',10,3), ('cat',16,3)]  def my_reduce(obj1, obj2):     return (obj1[0],max(obj1[1],obj2[1]),min(obj1[2],obj2[2]))

solution:

print [reduce(my_reduce, group)        _, group in groupby(sorted(pets), key=itemgetter(0))]

output:

[('cat', 16, 1), ('dog', 12, 1)]

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