[python] how to convert 2d list to 2d numpy array?

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?

np.array() is even more powerful than what unutbu said above. You also could use it to convert a list of np arrays to a higher dimention array, the following is a simple example:

aArray=np.array([1,1,1])

bArray=np.array([2,2,2])

aList=[aArray, bArray]

xArray=np.array(aList)

xArray's shape is (2,3), it's a standard np array. This operation avoids a loop programming.

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

I am using large data sets exported to a python file in the form

XVals1 = [.........] 
XVals2 = [.........] 

Each list is of identical length. I use

>>> a1 = np.array(SV.XVals1)

>>> a2 = np.array(SV.XVals2)

Then

>>> A = np.matrix([a1,a2])