[issue34778] Memoryview for column-major (f_contiguous) arrays from bytes impossible to achieve

[Stefan Krah]

Stefan Krah <stefan at bytereef.org> added the comment:

It seems reasonable to support f-contiguous for cast() and tobytes().
For tobytes() it's implemented in the issue that Antoine linked to.


General support for strides in cast(), i.e. a zero-copy view for
non-contiguous arrays does not seem possible because buf.ptr is
moved around. Even NumPy does not support that:

>>> x = np.array([1,2,3])
>>> x.view('B')
array([1, 0, 0, 0, 0, 0, 0, 0, 2, 0, 0, 0, 0, 0, 0, 0, 3, 0, 0, 0, 0, 0,
       0, 0], dtype=uint8)
>>> 
>>> x[::-1].view('B')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: To change to a dtype of a different size, the array must be C-contiguous
>>> 
>>> y = x.astype('B')
>>> y.flags['OWNDATA'] # It's a copy.
True

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue34778>
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