Select every other n rows in ArcGIS for Desktop?

Question

I am trying to select n rows then skip n rows and then select the next n rows until the completion of all rows in a feature class in a file-geodatabase. Below is an example where n =3:

1. Select
2. Select
3. Select
4. Not selected
5. Not selected
6. Not selected
7. Select
8. Select
9. Select

I basically need to make a selection like this and populate the rows that are selected.

Answer 1

Here is a small python script which will serve your purpose.

# required import
import arcpy

# inputs
# feature class path
fc = r'C:\GISData\File Geodatabase.gdb\feature_class'

# interval
interval = 3

# --------------------- script ------------------------- #
selected_oid = []
ready_to_add = False
interval = abs(interval)

fc = arcpy.MakeFeatureLayer_management(fc, r'in_memory\fc_name')
with arcpy.da.SearchCursor(fc, 'OID@') as cur:
    for i, row in enumerate(cur):
        if i % interval == 0:
            ready_to_add = not ready_to_add
        if ready_to_add:
            selected_oid.append(unicode(row[0]))

# where clause to select by attribute value
where = 'OBJECTID in ({})'.format(', '.join(selected_oid))

# selected features as required
selected_fc = arcpy.SelectLayerByAttribute_management(fc, "NEW_SELECTION", where)

Hope, this will help :)