Antoine Pitrou <solip...@pitrou.net> wrote: > Only if the original object is itself mutable, otherwise the memoryview > is read-only. > > I would propose the following algorithm: > 1) try to calculate the original object's hash; if it fails, consider > the memoryview unhashable (the buffer is probably mutable)
With slices or the new casts (See: http://bugs.python.org/issue5231, implemented in http://hg.python.org/features/pep-3118#memoryview ), it is possible to have different hashes for equal objects: >>> b1 = bytes([1,2,3,4]) >>> b2 = bytes([4,3,2,1]) >>> m1 = memoryview(b1) >>> m2 = memoryview(b2)[::-1] >>> m1 == m2 True >>> hash(b1) 4154562130492273536 >>> hash(b2) -1828484551660457336 Or: >>> a = array.array('L', [0]) >>> b = b'\x00\x00\x00\x00\x00\x00\x00\x00' >>> m_array = memoryview(a) >>> m_bytes = memoryview(b) >>> m_cast = m_array.cast('B') >>> m_bytes == m_cast True >>> hash(b) == hash(a) Traceback (most recent call last): File "<stdin>", line 1, in <module> TypeError: unhashable type: 'array.array' Stefan Krah _______________________________________________ Python-Dev mailing list Python-Dev@python.org http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
