topic Re: Search Cursor Structure in Python Questions

Search Cursor Structure

JamesSmith7 — Wed, 07 Aug 2013 13:29:06 GMT

I am using a SearchCursor to return a value from a selected attribute field. But, the cursor does not work or create an error. The ValueGain filed is a Long field type that is has not been set to a string. I am only using the SearchCursor to return a value in the tool dialog window.

arcpy.SelectLayerByAttribute_management(lyr, "NEW_SELECTION", whereClause) df.extent = lyr.getSelectedExtent() df.scale = df.scale*1.1 arcpy.AddMessage(str(whereClause))  cursor = arcpy.da.SearchCursor("Land", ["ValueGain"]) for row in cursor:  arcpy.AddMessage(str(ValueGain))  del row  del cursor

Re: Search Cursor Structure

ArkadiuszMatoszka — Wed, 07 Aug 2013 13:39:59 GMT

Hi,

When using arcpy.da.SearchCursor() each row is returned as list of values, correct call to get attribute value for row would be:

arcpy.SelectLayerByAttribute_management(lyr, "NEW_SELECTION", whereClause)  df.extent = lyr.getSelectedExtent()  df.scale = df.scale*1.1  arcpy.AddMessage(str(whereClause))   cursor = arcpy.da.SearchCursor("Land", ["ValueGain"])  for row in cursor:   arcpy.AddMessage(str(row[0])) # row[0] = first element of list that represents row  del row  del cursor

In case from your code:

arcpy.AddMessage(str(ValueGain))

ValueGain is unassigned variable, so you will get error.
Regards
Arek

Re: Search Cursor Structure

JamesSmith7 — Wed, 07 Aug 2013 13:43:26 GMT

Thanks for the quick response. Your suggestion worked.

Re: Search Cursor Structure

ChrisSnyder — Wed, 07 Aug 2013 15:17:26 GMT

each row is returned as list of values

To be more precise, each row is returned as a Python tuple... which is similar to a Python list, but one that can't be rearanged/sorted (aka an imutable list).

In Python:

tupleExample = (1,2,3,4)
listExample = [1,2,3,4]