How can I sort a list of dictionary by two keys, in which the second key should be sorted in descending order

Question

How can I sort a list of dictionary by two keys, in which the second key should be sorted in descending order. I have a list which contains a number of dictionaries, the format is:

result = [{'so':ABC,'so_value':123.0,'inv':'ADV-025'},
{'so':PQR,'so_value':19.0,'inv':'908025'}]

I want to sort the list by keys 'so' (ascending) and 'inv'(descending). How can I do this with itemgetter in python?

EDIT:

I have tried the following but it will sort only by ascending order. result = sorted(result, key=itemgetter('so', 'inv'))

@Christian I have tried the following but it will sort only by ascending order. result = sorted(result, key=itemgetter('so', 'inv')) — Gopakumar N G, Jan 03 '14 at 06:00
@GopakumarNG Add that as well to the question, otherwise this might be closed for no effort. — thefourtheye, Jan 03 '14 at 06:02
Note that in the above SO post I've said this is a duplicate of, the accepted answer provides a method to sort by an **arbitrary** number of keys, or which some can be "negated" (reversed) by prepending the key with a - (minus) sign. This I believe covers your case completely — three_pineapples, Jan 03 '14 at 06:03

HSquirrel · Answer 1 · 2014-01-03T10:24:03.493

I'd write my own compare function, so the cmp argument in sorted

Example (sorted on so ascending first, and on inv descending second):

from operator import itemgetter

input = [{'so':'PQR','so_value':19.0,'inv':'908025'},{'so':'ABC','so_value':123.0,'inv':'ADV-025'}]

def compare(x, y):
    (xso, xinv) = x
    (yso, yinv) = y
    socmp = cmp(xso,yso) #compare so
    if socmp == 0: #if so are equal, compare inv
        return -cmp(xinv, yinv) #minus for descending order
    else:
        return socmp

print sorted(input, cmp=compare, key=itemgetter('so','inv'))

Note that this is basically a simplified and less general version of the one in the post referenced by three_pineapples. If you understand this, I'd advise you to look at that link for a more general solution.

How can I sort a list of dictionary by two keys, in which the second key should be sorted in descending order

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