[gdal-dev] Issue with python bindings.

[Ivan Willig]

Thanks Jason,
I will add my examples when I get a chance.

Ivan Willig




On Tue, Oct 26, 2010 at 10:59 AM, Jason Roberts <jason.roberts at duke.edu>wrote:

>  Ivan, Frank,
>
>
>
> A month ago I started a gotchas page with Even Rouault that discusses this
> issue: http://trac.osgeo.org/gdal/wiki/PythonGotchas. If you have a
> moment, please consider adding your examples as other cases that cause the
> lifetime problem. Also (Frank) if there is any general advice you wish to
> add, it would be greatly appreciated.
>
>
>
> Best,
>
> Jason
>
>
>
> *From:* gdal-dev-bounces at lists.osgeo.org [mailto:
> gdal-dev-bounces at lists.osgeo.org] *On Behalf Of *Ivan Willig
> *Sent:* Tuesday, October 26, 2010 10:54 AM
> *To:* Frank Warmerdam
> *Cc:* gdal-dev at lists.osgeo.org
> *Subject:* Re: [gdal-dev] Issue with python bindings.
>
>
>
> Thanks Frank. That seems to be the issue. Whats the rule about this how
> long you should keep a reference. For example this causes the same issue.
>
>
>
> ds.GetLayer().GetFeature(0).GetGeometryRef().GetEnvelope()
>
>
>
> Which I am going to guess is because I should keep a reference to the
> geometry. Correct?
>
>
>  Ivan Willig
>
>
>
>
>  On Tue, Oct 26, 2010 at 10:44 AM, Frank Warmerdam <warmerdam at pobox.com>
> wrote:
>
> Ivan Willig wrote:
>
> Hi list,
> I am having an issues with using the python swig based bindings. I am on
> Fedora 13 using the default gdal rpm, which is at version 1.6.2. My issue is
> when i stack method calls.  For example when I do the following:
> ogr.Open("/home/ivan/dev/bigapps/data/nyco.shp").GetLayer().GetFeature(0)
>
>
> I get a Segmentation fault. Here are the results of strace
> http://paste.pocoo.org/show/281682/. What am I doing wrong? Should I just
> hand compile a new version of gdal? Or is this not an advised usage of the
> python bindings? A limitation in swig? Thanks for your help.
>
>
>
> Ivan,
>
> I believe the problem is object lifetimes.  Keep a reference to the
> datasource around until you are done with the feature(s).
>
> ds = ogr.Open("/home/ivan/dev/bigapps/data/nyco.shp")
> feat = ds.GetLayer().GetFeature(0)
> ...
> feat = None
> ds = None
>
> Best regards,
> --
>
> ---------------------------------------+--------------------------------------
> I set the clouds in motion - turn up   | Frank Warmerdam,
> warmerdam at pobox.com
> light and sound - activate the windows | http://pobox.com/~warmerdam
> and watch the world go round - Rush    | Geospatial Programmer for Rent
>
>
>
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