按优先级在python中的列排序矩阵

Question

i have the following matrix:

catch = [['fc', 2, 12, 2], 
 ['abcd', 1, 2, 0], 
 ['ab', 1, 0, 0], 
 ['cf', 1, 13, 0], 
 ['fc', 1, 14, 0], 
 ['f', 1, 11, 0]] 

and i want this matrix to be ordered by the fourth columns firstly (index 3), when the values of the fourth column are equals, order by the lenght of the string in the first column (index 0).

i just used

catch.sort(key=lambda x: x[3]) 

to sort the matrix by fourth column

Answer 1

Just make your key function return a tuple:

catch.sort(key=lambda x: (x[3], len(x[0]))) 

This works because two tuples are compared item by item, starting from index 0, stopping as soon as a difference is found (or one of the tuples runs out of items, in which case the longer tuple is considered to be larger, but that won't be relevant here, since our tuples all have a length of 2).