[Qgis-user] use Binary (Blob) in writeAsVectorFormat

[chris hermansen]

Hugh and list;

On Fri, Feb 3, 2023 at 11:41 AM Hugh Kelley via QGIS-User <
qgis-user at lists.osgeo.org> wrote:

> to follow up as I continue to work on this,
>
> I mistakenly understood the attribute type "binary" as a Boolean, but I
> think it's in fact an arbitrary value stored as binary. That is to say, not
> necessarily True/False or 0/1 but a series of 0/1's storing a value.
>
> If I can save it to the shapefile that would be great but I'm going to
> work on filtering those attributes out of what's saved as that's an
> acceptable solution too I think.
>
> On Fri, Feb 3, 2023 at 2:24 PM Hugh Kelley <hghklly at gmail.com> wrote:
>
>> Hi,
>>
>> I'm attempting to use pyqgis to export a few things to shapefile.
>>
>> the code below is working well except that a few of the attributes are
>> incompatible with shapefiles (amazing) lack of a binary datatype.
>>
>> ```py
>> pathToFile = "C:/Users/hkelley/Downloads/test_exports/
>>
>> layers = QgsProject.instance().mapLayers()
>>
>> for layer_id, layer in layers.items():
>>     print(layer.name())
>>     QgsVectorFileWriter.writeAsVectorFormat( layer,  pathToFile+
>> layer.name() + ".shp", "utf-8", layer.crs(), driverName="ESRI Shapefile"
>> )
>> ```
>>
>> I see in the manual export options that I can check a box telling the
>> export process to use "Use Binary (BLOB)". Image linked below for clarity
>> [0]
>>
>> I haven't yet figured out how to pass that option to writeAsVectorFormat.
>>
>> any suggestions?
>>
>> Iv'e had a pretty thorough look through the docs for writeAsVctorFormat,
>> is the solution related to
>> QgsVectorFileWriter.BoolOption(QgsVectorFileWriter.BoolOption)?
>>
>>
Have you looked at this https://en.wikipedia.org/wiki/.dbf to understand
how attributes are stored in .dbf files?

In particular there you will see this comment:

*All field data is ASCII. Depending on the field's type, the application
imposes further restrictions: *

Does this help?
-- 
Chris Hermansen · clhermansen "at" gmail "dot" com

C'est ma façon de parler.
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