Is there a way to count the records in a feature layer?

Question

I need to display several layers from the same feature class using definition queries for different systems and using the same template for different projects. While I have created a script that can automatically produce these layers in an MXD, the definition query will often reduce number of records to zero for certain systems, eliminating the need for it as a layer. I would like to use an IF statement with arcpy.mapping.RemoveLayer to automatically remove those layers that do not return results, but not sure which functions may be able to do this. I have looked into using SearchCursor but do not otherwise know how to identify the number of records in the attribute database for a particular layer.

JoshuaBixby · Answer

Both techniques will/do work, but in my experience the performance is not identical between the two.  For small to medium datasets (~100,000 records or less), the performance can be quite similar with the arcpy.da.SearchCursor and arcpy.GetCount_management.  For larger datasets, I have seen GetCount outperform cursors by 3 to 10 times.

Jason Scheirer​ speaks to why using a GP tool is faster than a Python cursor with larger datasets:  Re: How to determine number of records using arcpy.da.SearchCursor​.

JakeSkinner · Answer

Hi John,

Matthew and Stephen suggestions are right on track.  Either using the Search Cursor, or the Get Count will be identical in performance.  Example using Search Cursor:

mxd = arcpy.mapping.MapDocument(r"C:\Projects\Municipality.mxd")
df = arcpy.mapping.ListDataFrames(mxd)[0]
        list = []
        with arcpy.da.SearchCursor(lyr, ["OID@"], "OBJECTID > 0") as cursor:
                for row in cursor:
                        list.append(row[0])
        del cursor
        count = len(list)
        if count == 0:
          .....                     
del mxd

Example using Get Count:

mxd = arcpy.mapping.MapDocument(r"C:\Projects\Municipality.mxd")
df = arcpy.mapping.ListDataFrames(mxd)[0]

for lyr in arcpy.mapping.ListLayers(mxd, "*", df):
       result = arcpy.GetCount_management(lyr)
       count = int(result.getOutput(0))
       if count == 0:
         .....
del mxd

StephenBarrow · Answer

Would arcpy.GetCount_management() help?