I have a list of lists:
[[12, 'tall', 'blue', 1], [2, 'short', 'red', 9], [4, 'tall', 'blue', 13]]
If I wanted to sort by one element, say the tall/short element, I could do it via
s = sorted(s, key = itemgetter(1)).
If I wanted to sort by both tall/short and colour, I could do the sort twice, once for each element, but is there a quicker way?
A key can be a function that returns a tuple:
s = sorted(s, key = lambda x: (x, x))
Or you can achieve the same using
itemgetter (which is faster and avoids a Python function call):
import operator s = sorted(s, key = operator.itemgetter(1, 2))
And notice that here you can use
sort instead of using
sorted and then reassigning:
s.sort(key = operator.itemgetter(1, 2))
I'm not sure if this is the most pythonic method ... I had a list of tuples that needed sorting 1st by descending integer values and 2nd alphabetically. This required reversing the integer sort but not the alphabetical sort. Here was my solution: (on the fly in an exam btw, I was not even aware you could 'nest' sorted functions)
a = [('Al', 2),('Bill', 1),('Carol', 2), ('Abel', 3), ('Zeke', 2), ('Chris', 1)] b = sorted(sorted(a, key = lambda x : x), key = lambda x : x, reverse = True) print(b) [('Abel', 3), ('Al', 2), ('Carol', 2), ('Zeke', 2), ('Bill', 1), ('Chris', 1)]