How to sort a list of lists by a specific index of

问题:

I have a list of lists. For example,

[
[0,1,\'f\'],
[4,2,\'t\'],
[9,4,\'afsd\']
]

If I wanted to sort the outer list by the string field of the inner lists, how would you do that in python?

回答1:

This is a job for itemgetter

>>> from operator import itemgetter
>>> L=[[0, 1, \'f\'], [4, 2, \'t\'], [9, 4, \'afsd\']]
>>> sorted(L, key=itemgetter(2))
[[9, 4, \'afsd\'], [0, 1, \'f\'], [4, 2, \'t\']]

It is also possible to use a lambda function here, however the lambda function is slower in this simple case

回答2:

in place

>>> l = [[0, 1, \'f\'], [4, 2, \'t\'], [9, 4, \'afsd\']]
>>> l.sort(key=lambda x: x[2])

not in place using sorted:

>>> sorted(l, key=lambda x: x[2])

回答3:

Itemgetter lets you to sort by multiple criteria / columns:

sorted_list = sorted(list_to_sort, key=itemgetter(2,0,1))

回答4:

Like this:

import operator
l = [...]
sorted_list = sorted(l, key=operator.itemgetter(desired_item_index))

回答5:

multiple criteria can also be implemented through lambda function

sorted_list = sorted(list_to_sort, key=lambda x: (x[1], x[0]))

回答6:

I think lambda function can solve your problem.

old_list = [[0,1,\'f\'], [4,2,\'t\'],[9,4,\'afsd\']]

#let\'s assume we want to sort lists by last value ( old_list[2] )
new_list = sorted(old_list, key=lambda x: x[2])

#Resulst of new_list will be:

[[9, 4, \'afsd\'], [0, 1, \'f\'], [4, 2, \'t\']]

回答7:

array.sort(key = lambda x:x[1])

You can easily sort using this snippet, where 1 is the index of the element.

回答8:

More easy to understand (What is Lambda actually doing):

ls2=[[0,1,\'f\'],[4,2,\'t\'],[9,4,\'afsd\']]
def thirdItem(ls):
    #return the third item of the list
    return ls[2]
#Sort according to what the thirdItem function return 
ls2.sort(key=thirdItem)