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Error when assigning a non-const memoryview to the copy of a const memoryview #2134

lesteve opened this issue Mar 8, 2018 · 1 comment


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lesteve commented Mar 8, 2018

I have a const memoryview and I am trying to create a non-const memoryview by copying it. Naively I would expect it to be possible. Here is a snippet that reproduces the problem:

import numpy as np

cdef const double[:] ro = np.ones(3)
cdef double[:] rw = ro.copy()

The error I get:

Memoryview 'const double[::1]' not conformable to memoryview 'double[:]'.

If I read the error correctly it seems like ro.copy() type is still const.

A bit more context: I am trying out cython 0.28b1 and experimenting with const memoryviews in a scikit-learn context.

Side-comment: it is a slight variation of 6704d23 where instead of creating rw and then replacing the values by using rw[:] = ..., I am trying to do it in one line (which feels like the thing you would write in practice).

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lesteve commented Mar 28, 2018

Nice, thanks a lot for the fix!

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