Value Error when adding adding a layer in ArcGIS Pro arcpy script

Question

In a script, I'm creating a feature layer and trying to add it to a map in ArcGIS Pro 2.3.0. When I try to add it though, I get a ValueError. Any ideas why and how to fix it? m is the map object. The layer is created.

FWIW, I'm running the script in Spyder, Python 3.6.6, which I installed (maybe correctly, maybe not) in the default ArcGIS Pro environment. It seems to recognize the arcpy module, although there's no intellisense.

aprx = arcpy.mp.ArcGISProject(prj)
m = aprx.listMaps()[0]
target = m.listLayers('Cities Villages Twps')[0]
try:    
    target.definitionQuery = "NAME = 'Chicago'"
    arcpy.CopyFeatures_management(target, 'GPP')
    arcpy.MakeFeatureLayer_management('GPP', "Area501")
    print(type("Area501"))   # str
    print(type(Area501))     # NameError: name 'Area501' is not defined
    print(type(Area501[0]))  # NameError: name 'Area501' is not defined
    m.addLayer(Area501[0])   # NameError: name 'Area501' is not defined   

except Exception:
    print(arcpy.GetMessages())
    print('\n')
    tb.print_exc(limit=1, file=sys.stdout)

del aprx

Answer 1

It's failing because you're passing in a string to the addLayer function and hoping the method will resolve to the layer you created. In short, it wont. You'll need to be more explicit in what you pass addLayer - the actual layer from the result. In the below code I know that grabbing the first index ([0]) gets the layer object.

fooResult = arcpy.MakeFeatureLayer_management('Points', "fooName")
type("fooName")
# <class 'str'>
type(fooResult )
# <class 'arcpy.arcobjects.arcobjects.Result'>
type(fooResult [0])
# <class 'arcpy._mp.Layer'>

p = arcpy.mp.ArcGISProject("current")
m = p.listMaps()[0]
m.addLayer("fooName")
# value error  - its a string
m.addLayer(fooResult)
# value error  - its a result object
m.addLayer(fooResult[0])
# [<arcpy._mp.Layer object at 0x000002D941E296D8>]