Explain me this code! What is a[x] value?

Question

a = [3,2,0,1]
b = [1,0,3,2]

b.sort(key=lambda x: a[x])
Print(b)

#prints
[2,3,1,0]

Answer 1

From how I understand, b is the “key” and a is the list being changed. The first item in b is 1, and a[1] is 2. The second item is 0, and a[0] is 3. The third item is 3, and a[3] id 1. The last item is 2, and a[2] is 0. So then b now is [2, 3, 1, 0];

Answer 2

What Rowsej said, but exactly the other way round.

b is sorted, a is used as a key.

b = [1, 0, 3, 2]

For the first element (1), the key is a[1], which is 2. So the value 1 will have the index 2 in the sorted list:

sorted b = [?, ?, 1, ?]

For the second element (0), the key is a[0], which is 3. So the value 0 will have the index 3 in the sorted list:

sorted b = [?, ?, 1, 0]

For the third element (3), the key is a[3], which is 1. So the value 3 will have the index 1 in the sorted list:

sorted b = [?, 3, 1, 0]

For the fourth element (2), the key is a[2], which is 0. So the value 2 will have the index 0 in the sorted list:

sorted b = [2, 3, 1, 0]

Answer 3

Thank you Anna

Answer 4

Thanks.. Rowsej