ArcGIS 10.3.x Python 3.4 cannot delete layer

FilipKrál

Hello,

I need to create a layer, then delete it and then create a layer of the same name again. The script below works as expected in Python 2.7 32 bit, but fails in Python 3.4 64 bit in ArcGIS 10.3.1.

Can anyone explain why?

import arcpy

in_fc=r'C:\dump.gdb\zn3_0'
w = "STATION=3001"
lrname = 'lr1'

# create a layer
lr = arcpy.management.MakeFeatureLayer(in_fc, lrname, w).getOutput(0)
print(arcpy.Exists(lrname)) # True

# delete the layer
arcpy.management.Delete(lr)
arcpy.management.Delete(lrname)
del lr
print(arcpy.Exists(lrname)) # should be False but returns True in Python 3.4!

# create the layer again fails in Python 3.4
lr = arcpy.management.MakeFeatureLayer(in_fc, lrname, w).getOutput(0)
# ERROR 000725: Output Layer: Dataset lr1 already exists.

# and indeed the layer still exists after the error
print(arcpy.Exists(lrname)) # True
arcpy.management.GetCount(lrname).getOutput(0) # 1

Filip.

FilipKrál

Hi,

I tried this in ArcGIS Pro 1.3 with Python 3.4.4 and it behaves well. The key thing is to delete the reference to the layer object when you are done with it ('del lr')!

So the right way to create and delete a layer is

in_fc, w =r'C:\temp\fc.shp', "FID < 3"
lr = arcpy.management.MakeFeatureLayer(in_fc, 'lr1', w).getOutput(0)
arcpy.management.Delete(lr)
del lr

Alternatively, wrapping the part of your where the layer is created, used, and then delted in a function *should* also resolve the issue because (as far as I know) the reference to the layer object *should* be garbage collected by Python when the function finishes.

The code below shows more details. It creates a layer, deletes the layer, then it creates and deltes the layer again. You would not do this in practice but it's important to be able to copletely delete layers in Python scripts (e.g. when using arcpy.management.SelectLayerByLocation in a loop). The bottom line is, use the 'del' statement.

import arcpy

in_fc=r'C:\temp\fc.shp'
w = "{0} < 3".format(arcpy.Describe(in_fc).OIDFieldName)
lrname = 'lr1'

# create a layer
lr = arcpy.management.MakeFeatureLayer(in_fc, lrname, w).getOutput(0)
print(arcpy.Exists(lr)) # True
print(arcpy.Exists(lrname)) # True
print(type(lr)) # <class 'arcpy._mp.Layer'>

# delete the layer
arcpy.management.Delete(lr)
print(arcpy.Exists(lr)) # True
print(arcpy.Exists(lrname)) # True

del lr

print(arcpy.Exists(lrname)) # False
#print(arcpy.Exists(lr)) # we deleted variable lr using 'del lr' so we can't refer to it

# create and delete the layer again
lr = arcpy.management.MakeFeatureLayer(in_fc, lrname, w).getOutput(0)
print(arcpy.Exists(lrname)) # True
print(arcpy.management.GetCount(lrname).getOutput(0)) # 3
arcpy.management.Delete(lr)
del lr

Filip.