Cython: Convert memory view to NumPy array

Question

How to convert a typed memoryview to an NumPy array in cython? The docs have

cimport numpy as np import numpy as np  numpy_array = np.asarray(<np.int32_t[:10, :10]> my_pointer) 

I took this for my case

np.asarray(<np.float_t[:, :]> my_memview) 

Using this the compiler tells me:

Can only create cython.array from pointer or array 

Copying or not is not so decicive. I couldn't find any help on this.

Answer 1

You should just be able to use np.asarray directly on the memoryview itself, so something like:

np.asarray(my_memview) 

should work. For example if your cython source file contains this:

import numpy as np cimport numpy as np def test(double[:,:] x):     print type(x)     print type(np.asarray(x)) 

Then after compiling it, you should be able to do the following from the python side:

a = np.random.normal(size=(5,5)) test(a) 

Which produces the following output:

<type '_cython_magic_0182fca918bfa3618c3553e51b13e8ba._memoryviewslice'> <type 'numpy.ndarray'> 

Note: I'm using the cythonmagic extension for IPython.