topic Re: Determine if valid query returns records in Python Questions

Determine if valid query returns records

JohnDye — Thu, 09 Jan 2014 14:08:13 GMT

What's the most elegant way to determine if a valid SQL Query (Attribute Query or Definition Query) returns no records?

I wrote this little function to just take a layer on disk, apply a definition query and update the name of the layer then pop it into the dataframe, but before I do that I want to validate that the definition query actually returned some records.

def createDerivedLayer(SourceLayer, UpdateName, DefinitionQuery = ""):     """     Creates a new in-memory Layer in the ArcMap Table of Contents derived from an     existing Layer on disk or in the ArcMap Table of Contents as referenced by the 'SourceLayer'     argument, and pastes the DerivedLayer into the Table of Contents.     Optionally applies a Definition Query to the newly Dervied Layer.     """     SourceLayer = arcpy.mapping.Layer(str(SourceLayer))     DerivedLayer = SourceLayer     DerivedLayer.name = str(UpdateName)     if DefinitionQuery:         DerivedLayer.definitionQuery = str(DefinitionQuery)     arcpy.mapping.AddLayer(df, DerivedLayer, "AUTO_ARRANGE")     arcpy.RefreshTOC()     arcpy.RefreshActiveView()

ICan anyone think of a way to see if 'DerivedLayer' has at least 1 records without having to go through the entire dataset? I think I'm just overthinking this...probably a very simply solution I'm overlooking

Re: Determine if valid query returns records

JamesCrandall — Thu, 09 Jan 2014 14:21:22 GMT

This works on a Feature Layer. See if it will work for you!

rowcount = int(str(arcpy.GetCount_management("DerivedLayer")))  if rowcount > 0:    'we have rows, do something with them! else:    'no rows in the DerivedLayer, I guess exit?    return

Re: Determine if valid query returns records

JohnDye — Sat, 11 Dec 2021 07:12:27 GMT

This works on a Feature Layer. See if it will work for you!

rowcount = int(str(arcpy.GetCount_management("DerivedLayer")))

if rowcount > 0:
   'we have rows, do something with them!
else:
   'no rows in the DerivedLayer, I guess exit?
   return

Exactly what I needed! Thanks James!!