Select By Attributes Based on Unique Value in Shapefile gives ERROR 000840?

Question

Using ArcGIS 10.4.1 and Arcpy I am trying to select a shapefile by it attributes and create new feature class based on unique values like

import arcpy
from arcpy import env

def unique_values(table , field):
    with arcpy.da.SearchCursor(table, [field]) as cursor:
        return sorted({row[0] for row in cursor})

uniques = unique_values(r'D:/GIS/Roads.shp' , 'fclass')
for unique in uniques:
    arcpy.SelectLayerByAttribute_management (r'D:/GIS/Roads.shp', "NEW_SELECTION", " 'fclass' = '"+unique+"' ")
    print (unique)

but I am getting this error message

Message File Name Line Position Traceback
11
SelectLayerByAttribute C:\Program Files (x86)\ArcGIS\Desktop10.4\ArcPy\arcpy\management.py 7182
ExecuteError: Failed to execute. Parameters are not valid. The value cannot be a feature class ERROR 000840: The value is not a Raster Layer. ERROR 000840: The value is not a Mosaic Layer. Failed to execute (SelectLayerByAttribute).

Answer 1

The tool Select Layer by Attribute requires a layer, not a feature class. A shapefile is a feature class.

You either need to use a layer from the Table of Contents in ArcMap, or create a layer using Make Feature Layer tool.

for unique in uniques:
    arcpy.MakeFeatureLayer_management(r'D:/GIS/Roads.shp', 'myLayer')
    arcpy.SelectLayerByAttribute_management ('myLayer', "NEW_SELECTION", " 'fclass' = '"+unique+"' ")
    print (unique)

Take a look at the documentation for Select Layer by Attribute