gh-78959: Add order parameter to memoryview.cast()

[serhiy-storchaka]

memoryview.cast() now accepts a keyword-only order parameter. With a multidimensional shape, order='F' returns a zero-copy Fortran-contiguous (column-major) view of a flat buffer, while order='C' (the default) keeps the current C-contiguous behavior. This mirrors the order argument of memoryview.tobytes() and makes it possible to interface with column-major libraries from pure Python without copying.

>>> buf = bytes(range(6))
>>> y = memoryview(buf).cast('B', shape=[3, 2], order='F')
>>> y.f_contiguous
True
>>> y.tolist()
[[0, 3], [1, 4], [2, 5]]

Only 'C' and 'F' are accepted; anything else raises ValueError, and non-single-character values raise TypeError. Unlike memoryview.tobytes(), None is not accepted, since the default already means 'C'.

• Issue: Memoryview for column-major (f_contiguous) arrays from bytes impossible to achieve #78959

[read-the-docs-community]

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3 files changed

± library/stdtypes.html
± whatsnew/3.16.html
± whatsnew/changelog.html