Creating Matrices using Numpy

Here are two ways of creating 2d-array:

1) By converting a list of lists (or tuples) into an array:

>>> x = N.array([[1,2,3], [4,5,6]])
>>> x
array([[1, 2, 3],
       [4, 5, 6]])

2) Using the zeros method to create a matrix with 5 rows and 5 columns

>>> x = N.zeros((5,5))
>>> print x
[[ 0.  0.  0.  0.  0.]
 [ 0.  0.  0.  0.  0.]
 [ 0.  0.  0.  0.  0.]
 [ 0.  0.  0.  0.  0.]
 [ 0.  0.  0.  0.  0.]]

The shape of a matrix can be queried like this.

>>> x.shape
(5, 5)

Individual elements can be accessed and set using this syntax:

>>> x = N.array([[1,2,3], [4,5,6]])
>>> x[0,0]
1
>>> x[0,1]
2
>>> x[0,2]
3
>>> x[:,0]
array([1, 4])
>>> x[0, :]
array([1, 2, 3])