Two dimensional array in python

Question

I want to know how to declare a two dimensional array in Python.

arr = [[]]  arr[0].append("aa1") arr[0].append("aa2") arr[1].append("bb1") arr[1].append("bb2") arr[1].append("bb3") 

The first two assignments work fine. But when I try to do, arr[1].append("bb1"), I get the following error:

IndexError: list index out of range. 

Am I doing anything silly in trying to declare the 2-D array?

Edit:
but I do not know the number of elements in the array (both rows and columns).

Answer 1

You do not "declare" arrays or anything else in python. You simply assign to a (new) variable. If you want a multidimensional array, simply add a new array as an array element.

arr = [] arr.append([]) arr[0].append('aa1') arr[0].append('aa2') 

or

arr = [] arr.append(['aa1', 'aa2'])