python matrix transpose and zip

Question

How to get the transpose of this matrix..Any easier ,algorithmic way to do this...

1st question:

 Input  a=[[1,2,3],[4,5,6],[7,8,9]]
 Expected output a=[[1, 4, 7], [2, 5, 8], [3, 6, 9]] 

2nd Question:

Zip gives me the following output said below,how can i zip when i dont know how many elements are there in the array,in this case i know 3 elements a[0],a[1],a[2] but how can i zip a[n] elements

 >>> zip(a[0],a[1],a[2])
 [(1, 4, 7), (2, 5, 8), (3, 6, 9)]

Answer 1

Use zip(*a):

>>> zip(*a)
[(1, 4, 7), (2, 5, 8), (3, 6, 9)]

How it works: zip(*a) is equal to zip(a[0], a[1], a[2]).