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

User · Answer

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])

User · Answer

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

User · Answer

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

User · Answer

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

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

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