Sort an array of tuples by product in python

Question

I have an array of 3-tuples and I want to sort them in order of decreasing product of the elements of each tuple in Python. So, for example, given the array

[(3,2,3), (2,2,2), (6,4,1)]

since 3*2*3 = 18, 2*2*2 = 8, 6*4*1 = 24, the final result would be

[(6,4,1), (3,2,3), (2,2,2)]

I know how to sort by, for example, the first element of the tuple, but I'm not sure how to tackle this. Any help would be greatly appreciated. Thanks!

Answer 1

Use the key argument of sorted/list.sort to specify a function for computing the product, and set the reverse argument to True to make the results descending rather than ascending, e.g.:

from operator import mul
print sorted([(3,2,3), (2,2,2), (6,4,1)], key=lambda tup: reduce(mul, tup), reverse=True)

Answer 2

In [176]: L = [(3,2,3), (2,2,2), (6,4,1)]

In [177]: L.sort(key=lambda (a,b,c):a*b*c, reverse=True)

In [178]: L
Out[178]: [(6, 4, 1), (3, 2, 3), (2, 2, 2)]

Answer 3

A simpler solution from my point of view:

a = [(3,2,3), (2,2,2), (6,4,1)]

def f(L):
    return L[0]*L[1]*L[2]

print sorted(a, key = f, reverse = True)

key must be a function that returns a value that will be used in order to sort the list

reverse is True because you want it ordered in decreasing order

Answer 4

>>> from operator import mul
>>> input_list = [(3,2,3), (2,2,2), (6,4,1)]
>>> input_list.sort(key=lambda tup: reduce(mul,tup)) 
>>> print input_list
[(2, 2, 2), (3, 2, 3), (6, 4, 1)]