[PYTHON MATRIX-SIG] pickle error on Win95

[Guido van Rossum]

> I've been waiting for somebody to notice this and properly castigate
> me for violating the beauty of pickle's text-only format.
> 
> There are some major size and speed savings to be realized by dumping
> large arrays in a binary format.  Since dumping 1 MB arrays to disk is
> not all that uncommon, these things are unfortunately an issue.

Agreed.  For large strings, I was going to add this (eventually) as a
speed up extension as well.

> This is the first time that anybody's noticed problems with the binary
> format, and it seems a simple enough matter to add warnings that
> matrices should only be pickled to binary format files.  Other than
> this, I've found the binary format to work quite well for archiving
> arbitrary objects that contain matrices across many platforms
> (big/little endian) and even for passing these objects across sockets.

You must've patched the pickle module, right?

> Anybody know a way I can add a check to the matrix pickling routines
> to determine if they're writing to/reading from a binary format file
> and raise an exception otherwise?

That's easy.  A file object has an attribute 'mode' which is the
read/write open mode.  Of course, pickle can also be used on pseudo
file objects (like StringIO) which don't have this attribute.

--Guido van Rossum <guido@CNRI.Reston.VA.US>
URL: <http://www.python.org/~guido/>

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