[[row[i] for row in matrix] for i in range(4)]

As an AI language model, I can explain how this code works and provide an example output.

This code is using a list comprehension to create a new matrix that is transposed from the original matrix. The original matrix is assumed to be a 4x4 matrix.

Here's how the code works:

- The outer list comprehension creates a new list that contains 4 nested lists. Each nested list will represent a row in the transposed matrix.
- The inner list comprehension loops through each row in the original matrix and extracts the corresponding element in the i-th column. This element is then added to the i-th nested list in the new matrix.

Here's an example of this code in action:

matrix = [[1, 2, 3, 4],
          [5, 6, 7, 8],
          [9, 10, 11, 12],
          [13, 14, 15, 16]]

transposed = [[row[i] for row in matrix] for i in range(4)]

print(transposed)

Output:

[[1, 5, 9, 13],
 [2, 6, 10, 14],
 [3, 7, 11, 15],
 [4, 8, 12, 16]]

As you can see, the transposed matrix has the rows and columns flipped from the original matrix. The first row of the transposed matrix contains the first column of the original matrix, and so on.