how to convert 2d list to 2d numpy array?

Question

I have a 2D list something like

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

and I want to convert it to a 2d numpy array. Can we do it without allocating memory like

numpy.zeros((3,3)) 

and then storing values to it?

Answer 1

Just pass the list to np.array:

a = np.array(a) 

You can also take this opportunity to set the dtype if the default is not what you desire.

a = np.array(a, dtype=...) 

Answer 2

just use following code

c = np.matrix([[1, 2, 3], [4, 5, 6], [7, 8, 9]]) matrix([[1, 2, 3],     [4, 5, 6],     [7, 8, 9]]) 

Then it will give you

you can check shape and dimension of matrix by using following code

c.shape

c.ndim