Question

matrix

is a list of lists with the same length. I’ve to return a dictionary of the form

{i:(l1[i],l2[i],...,lm[i])}

Where the key i is matched with a tuple the i’th elements
from each list.
Say

matrix=[[1,2,3,4],[9,8,7,6],[4,8,2,6]]

so the line:

>>> dict([(i,tuple(matrix[k][i] for k in xrange(len(matrix)))) for i in xrange(len(matrix[0]))])

does the job pretty well and outputs:

{0: (1, 9, 4), 1: (2, 8, 8), 2: (3, 7, 2), 3: (4, 6, 6)}

but fails if the matrix is empty: matrix=[]. The output should be: {}

How can i deal with this?

Answer 1

How about this instead:

>>> matrix = [[1,2,3,4],[9,8,7,6],[4,8,2,6]]
>>> dict(enumerate(zip(*matrix)))
{0: (1, 5, 4), 3: (4, 8, 6), 2: (3, 7, 2), 1: (2, 6, 8)}    
>>> matrix = []
>>> dict(enumerate(zip(*matrix)))
{}