Select by attribute on shapefile works when added to ToC but not when pointing to workspace

Question

I'm trying to build a script that uses select by attribute and select by location to do some operations on a couple of shapefiles containing a large amount of points and polygons. Preferably, I want to make it runnable without adding any files to Arcmap, but I can´t get Select by Attribute to work and I don´t understand why. Here´s an example:

arcpy.env.workspace = "C:/Projekt\Mitt_skolval/Test_adresser_skolor/"
fcs = arcpy.ListFeatureClasses()

print(fcs)

returns

[u'Adresser_18dec2020.shp', u'Skolskjutsomraden_4_5_2021.shp', u'Skolskjutsomraden_6_2021.shp', u'Skolskjutsomraden_7_9_2021.shp', u'Skolskjutsomraden_F_3_2021.shp']

If I then try this:

adresser = fcs[0]

arcpy.SelectLayerByAttribute_management(adresser, "NEW_SELECTION", "FID = 3")

It throws this error:

Runtime error  Traceback (most recent call last):   File "<string>", line 9, in <module>   File "c:\program files (x86)\arcgis\desktop10.8\arcpy\arcpy\management.py", line 7759, in SelectLayerByAttribute     raise e ExecuteError: 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.

Saying from what I understand that I can´t use Select by attribute on a shapefile, which is weird. HOWEVER, if I add the same shapefile to the ToC and run

arcpy.SelectLayerByAttribute_management(Adresser_18dec2020, "NEW_SELECTION", "FID = 3")

It works.

Why is this?

I know I can solve this by creating feature layers, but I want to avoid this if possible.

Answer 1

A selection cannot be made directly on a feature class or shapefile. It must be made on a feature layer. The ToC contains layers created when data is added to the map document, that is why you can do a selection on them.

Your script will need to include MakeFeatureLayer_management to perform the way you want. You can include your selection in the where_clause of the tool.