I'm trying to finish a script that select a polygon attribute by location using the arcpy call. Here is my code:

project = arcpy.GetParameter(0)

proj_layer = r'memory/' + str('proj')
arcpy.MakeFeatureLayer_management(project_path, proj_layer)

arcpy.AddMessage("PROJECT_NAME = '{}'".format(project))

arcpy.SelectLayerByAttribute_management(proj_layer, "NEW_SELECTION", "PROJECT_NAME = '{}'".format(project))

The variable project_path is the correct path and I know it is because I used a print statement to verify that. I'm thinking that it may be some issue with the expression because the output is:

PROJECT_NAME = 'spokane_test'
Failed script UUIDScript...
Traceback (most recent call last):
File "C:\Users\jhodg1\Desktop\Construction Dev\UUIDScript2.py", line 58, in <module>
arcpy.SelectLayerByAttribute_management(proj_layer, "NEW_SELECTION", "PROJECT_NAME = '{}'".format(project))
File "C:\Program Files\ArcGIS\Pro\Resources\ArcPy\arcpy\management.py", line 9727, in 
raise e
File "C:\Program Files\ArcGIS\Pro\Resources\ArcPy\arcpy\management.py", line 9724, in 
retval = convertArcObjectToPythonObject(gp.SelectLayerByAttribute_management(*gp_fixargs((in_layer_or_view, selection_type, where_clause, invert_where_clause), True)))
File "C:\Program Files\ArcGIS\Pro\Resources\ArcPy\arcpy\geoprocessing\_base.py", line 512, in <lambda>
return lambda *args: val(*gp_fixargs(args, True))
arcgisscripting.ExecuteError: ERROR 000358: Invalid expression
Failed to execute (SelectLayerByAttribute).

What happens is that the user is supposed to input the project name as a parameter and then I run the script which will then select the polygon based on its name. 'PROJECT_NAME' is the name of the field that I am querying in the 'project_path' layer and I know it exists and that I'm typing in the right name for the project name because I'm looking at the row so I know. Can anyone tell what I am doing wrong and what's making it print out "invalid expression"?

  • The back-end data source can affect SQL syntax, try using a file geodatabase feature class to make sure it isn't an issue with the memory workspace.
    – bixb0012
    Commented Mar 27, 2023 at 16:35
  • 1
    Strange name for layer. What 'memory' role here?
    – FelixIP
    Commented Mar 27, 2023 at 19:03
  • Why are you doing str('proj')? 'proj' is already a string. Commented Mar 27, 2023 at 23:28
  • 1
    What is project_path? Where is it defined? Commented Mar 27, 2023 at 23:29
  • 1
    Probably best to avoid having slash (/) or backslash () in the name of a layer, unless you really want to use group layer hierarchies. Commented Mar 27, 2023 at 23:33

1 Answer 1


I suggest you make a python variable called select_clause and set it to the embedded format expression as follows:

select_clause = "PROJECT_NAME = '{}'".format(project)

Then (temporarily print it) use it what was line 58 where the arcpy chokes on the string manipulation inside the parameter usage:

print ('Select Clause = ' + select_clause)
arcpy.SelectLay`erByAttribute_management(proj_layer, "NEW_SELECTION", select_clause)

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