[Numpy-discussion] Non-writeable default for numpy.ndarray
oliphant.travis at ieee.org
Fri Sep 29 11:55:25 CDT 2006
Tim Hochberg wrote:
> Francesc Altet wrote:
> It's not that the it's being built from ndarray, it's that the buffer
> that you are passing it is read only.
This is correct.
> In fact, I'd argue that allowing
> the writeable flag to be set to True in this case is actually a bug.
It's actually intentional. Strings used as buffers are allowed to be
writeable. This is an explicit design decision to allow pickles to load
without making 2 copies of the memory. The pickled string that Python
creates is used as the actual memory for loaded arrays.
Now, I suppose it would be possible to still allow this but be more
finnicky about when a string-used-as-the-memory can be set writeable
(i.e. we are the only reference to it). But, this would be a fragile
solution as well.
My inclination is to just warn users not to use strings as buffers
unless they know what they are doing. The fact that it is read-only by
default is enough of a guard against "accidentally" altering a string
you didn't want to alter.
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