[docs] [issue23756] Tighten definition of bytes-like objects

Martin Panter report at bugs.python.org
Fri Apr 3 13:37:55 CEST 2015


Martin Panter added the comment:

I’m sorry Stefan, I now realize my changes for len(view) were indeed wrong, and the original was much more correct. I still think the tobytes() and maybe tolist() documentation could be improved, but that is a separate issue to the bytes-like definition.

I am posting c-contig.v2.patch. Hopefully you will find it is truer to my original scope :)

* Removed changes to stdtypes.rst
* Scaled back changes in buffer.rst to only explain “C-contiguous”
* Tweaked glossary definition. Not all memoryview() objects are applicable.

David: The result of passing a Fortran array directly in a bytes-like context is typically BufferError. If this were relaxed, then we would get the inconsistency with tobytes().

>>> import _testbuffer, sys
>>> layout = [11, 21, 12, 22]
>>> fortran_array = _testbuffer.ndarray(layout, format="B", flags=0, shape=[2, 2], strides=[1, 2], offset=0)
>>> sys.stdout.buffer.write(fortran_array)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
BufferError: ndarray is not C-contiguous
>>> list(memoryview(fortran_array).tobytes())  # C-contiguous order!
[11, 12, 21, 22]

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Added file: http://bugs.python.org/file38815/c-contig.v2.patch

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