Sorting list of list based on Inner List's Multiple Integer elements [duplicate]

Question

I want to sort the list of list based on the two factors:

• PRIMARILY: list has to be sorted in ascending order based on the second element of each list in the list
• If there are cases wheres various list has same second elements then for those particular lists sorting has to be done in ascending order based on first element.

data_input: [ [78, 10], [130, 0], [10, 1], [100, 100], [2, 2], [1, 99], [100, 0] ]

for sorting based on first criterion I am using this code

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

but cannot think of any way to implement second criterion as well

Desired output :

• data_input: [ [100, 0], [130, 0], [10, 1], [2, 2], [78, 10], [1, 99], [100, 100] ]*

Answer 1

You can use sorted with itemgetter to specify the order in which items from the sublists must be fetched:

from operator import itemgetter

sorted(data_input, key=itemgetter(1,0))
# [[100, 0], [130, 0], [10, 1], [2, 2], [78, 10], [1, 99], [100, 100]]

Answer 2

Use a tuple as key argument to sorted:

data_input = [ [78, 10], [130, 0], [10, 1], [100, 100], [2, 2], [1, 99], [100, 0] ]

print(sorted(data_input, key=lambda x: (x[1], x[0])))
# [[100, 0], [130, 0], [10, 1], [2, 2], [78, 10], [1, 99], [100, 100]]

This basically asks Python to sort by x[1] and for same x[1], sort by x[0].