[gdal-dev] Adding field to Shapefile via Python

[Chaitanya kumar CH]

Mike,

A new field cannot be added to a feature definition while there are any
features based on that feature definition.
See the docs for OGRFeatureDefn::AddFieldDefn()
http://www.gdal.org/ogr/classOGRFeatureDefn.html#40e681d8464b42f1a1fac655f16ac3dd

On Fri, Mar 18, 2011 at 11:01 AM, Mike Toews <mwtoews at gmail.com> wrote:

> In a Python script, I am updating an exiting shapefile with data by
> adding a column. However, my changes don't seem to be saved. Here is
> what I have:
>
> from osgeo import ogr
> obs_file = 'myfile.shp'
>
> source = ogr.Open(obs_file, 1)
> layer = source.GetLayer()
> layer_defn = layer.GetLayerDefn()
>
> new_field = ogr.FieldDefn('MYFLD', ogr.OFTInteger)
> layer_defn.AddFieldDefn(new_field)
>
> source = None
>
> However, when I check the resulting file, I do not see the new field.
>
> I have also tried inserting the following (before "source=None")
>
> feature = layer.GetNextFeature()
> feature.GetField('EXIST') # an existing float field with data
> feature.SetField('EXIST', 111.1) # works
> feature.SetField('MYFLD', 123) # does nothing
> layer.SetFeature(feature)
>
> Which successfully updates the data in the existing field, but not the
> added field.
>
> Where did I go wrong? Thanks in advance.
>
> -Mike
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>



-- 
Best regards,
Chaitanya kumar CH.
/tʃaɪθənjə/ /kʊmɑr/
+91-9494447584
17.2416N 80.1426E
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