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I have a question regarding selections in ArcGIS for Desktop. Assumed I have one layer in ArcMap and I have selected two of five features.

Is it possible to get a list of all selected features by using Python?

It would be fine if there is a way to get one special (or all) attribute(s) of the selected features stored in a list that can be written into a txt file.

Is it possible to do this in ArcGIS for Desktop?

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3 Answers 3

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36

Any time you have a selection on a layer a cursor object will only return the selected rows.

for row in arcpy.SearchCursor("name_of_layer_with_selection"):
    print row.field1, row.field2
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  • 7
    But the problem though is that if you get all the features returned you don't know if ALL or NONE were selected. Commented Apr 21, 2014 at 14:01
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    Does this also apply to selected features in feature class ? Commented Sep 4, 2015 at 18:22
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the Describe function will also return a list. I am not sure if this is faster than the cursor method but I have fond this to be a useful tool. The resulting list is the object id's for the selection set.

import arcpy

aa = arcpy.Describe("someFC")
ss = aa.FIDset
tt = ss.split("; ")
Print tt

[u'1363', u'1364', u'1365', u'1367', u'1369', u'1370']
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4
  • Good solution too! Sadly I am not able to set two times the green heel. This solution makes the script also independent from different ArcGIS Versions, because in ArcGIS 10.1 the cursors are called in a different way than in ArcGIs 10.0 (ArcGIS 10.1 arcpy.da.SearchCursor, ArcGIS 10.0 arcpy.SearchCursor...). Commented Dec 31, 2012 at 20:38
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    Both cursor types are available at 10.1. You don't have to use the new arcpy.da cursors. Commented Dec 31, 2012 at 20:53
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    This answer gives a way to check for empty selection, which would prevent inadvertently calling a tool on an entire feature class when in fact it was zero features that happened to fulfill your selection criteria. Commented Oct 18, 2017 at 16:28
  • Great tip @Sam Flarity, this is a nice (faster?) alternative to using arcpy.SearchCursor or arcpy.da.SearchCursor Commented Jun 14, 2018 at 0:15
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Whether ArcGIS Desktop/ArcMap or ArcGIS Pro, the best approach for determining a selection set on a layer or table view is using the getSelectionSet() method of Layer - ArcGIS Pro | Documentation or Layer - ArcMap | Documentation.

Calling layer.getSelectionSet() is better than calling describe.FIDSet for both performance and functional reasons. On the performance side, having to instantiate a Describe object is an extra step and cost when one can get the same information from a layer directly. More importantly, getSelectionSet() recognizes the difference between no selection and a selection with no records whereas FIDSet returns the same empty string in both situations.

>>> arcpy.management.SelectLayerByAttribute(layer, 'NEW_SELECTION', "1=1")
<Result 'layer'>
>>> print(layer.getSelectionSet())
{1, 2, 3, 4, 5}

>>> arcpy.management.SelectLayerByAttribute(layer, 'NEW_SELECTION', "1=2")
<Result 'layer'>
>>> print(layer.getSelectionSet())
set()

>>> arcpy.management.SelectLayerByAttribute(layer, 'CLEAR_SELECTION')
<Result 'layer'>
>>> print(layer.getSelectionSet())
None
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