[Numpy-discussion] Problems casting object arrays to string type on Ubuntu
Tue Nov 24 09:58:29 CST 2009
Sorry I missed your message the first time around.
I suspect you're running into this bug:
This has been fixed in SVN r7514, (and thus 1.4 pre releases), so it's
not a platform difference.
The workaround (at the expense of performance, of course) is to cast to
a list then cast to a string array. I'm not sure if there's a better
(i.e. more performant) workaround. But you could (in your client code)
check for the version of Numpy and act accordingly.
Dan Yamins wrote:
> Really, no idea about this? (Sorry if my original email was unclear.)
> On Sat, Nov 21, 2009 at 3:27 PM, Dan Yamins <email@example.com
> <mailto:firstname.lastname@example.org>> wrote:
> Hi all,
> I'm having some issues casting object arrays to string type,
> especially on my Ubuntu installation. (Ubuntu Jaunty, 9.04, with
> Numpy v. 1.3.)
> With small arrays, the conversion is just wrong. With large
> arrays, there seems to be some memory corruption. Conversion to
> int or float (when appropriate) seems to work.
> For instance, here are some examples of errors with small arrays:
> >>> X = numpy.array([13,14],'object')
> >>> X.astype('|S2')
> array(['13', '\xb2'],
> >>> X.astype('int') #conversion to int or float seems to
> work fine
> array([13, 14])
> >>> X.astype(float)
> array([ 13., 14.])
> >>> X = numpy.array(['cat','bat'],'object')
> >>> X.astype('|S3')
> array(['cat', '\x00ba'],
> Large arrays:
> In : X = numpy.array(['cat','bat']*300000,'object')
> In : Y = X.astype('|S3')
> *** glibc detected *** /usr/bin/python: munmap_chunk(): invalid
> pointer: 0xb7cd5008 ***
> I do NOT have this problem with Numpy 1.4.0.dev7746, installed on
> my OSX 10.5.8 machine. There, everything seems to work fine.
> What's going on? I feel like I've seem some traffic about related
> issues on the list before, but I couldn't quite tell from reading
> the threads what the "final upshot" of the discussion was ...
> Is this something that was fixed in recent NumPy 1.4 releases, or
> is something about my Ubuntu vs. OSX installations? Generally
> speaking can I / should I be relying on casting from object arrays
> to do the "right" (or "intuitive") thing?
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