ArcPy script causing python.exe to stop working (memory issue?)

Question

I have a script written in Python that uses ArcPy to create maps of the kernel densities of thousands of datasets. Each dataset is relatively small, but there about 50,000 sets in total.

When I run my script, it stops after about 10-15 minutes and gives the "python.exe has stopped working" popup. The Windows 7 event viewer tells me it is an Exception Code 0x0000005, which appears to be an access violation. The datasets the code works on are not the same each time, so it is not a specific set that is causing the problem.

Watching the task manager when the script is running, I noticed that python.exe is increasing its memory usage every few seconds, which makes me believe there is a memory leak somewhere. I thought Python had garbage collection? Is there something that arcPy is doing?

EDIT: So I tracked down the part of my code causing the problem, but I don't know HOW it is leaking. I think I am cleaning everything up. Does anyone spot something I missed?

def makeMap(asno, isKdens):
try:
 mxd = arcpy.mapping.MapDocument("F:\\testFiles\\testMap.mxd") ###Reference to basemap document
 df = arcpy.mapping.ListDataFrames(mxd, "Layers")[0] ###Get data frame reference in var
 ##++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 if isKdens:
 ###Set up layer file
 lyrFile = arcpy.mapping.Layer(r"F:\\testFiles\\output\\AS_"+asno+"_KDens.lyr")
 ##++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 else:
 ###Set up layer file
 lyrFile = arcpy.mapping.Layer(r"F:\\testFiles\\output\\AS_"+asno+".lyr")
 lyrFile.visible = True
 ###Add layer file
 arcpy.mapping.AddLayer(df, lyrFile)
 ###ref added layer
 lyr = arcpy.mapping.ListLayers(mxd)[0]
 lyr.visible = True
 #If this is a raw map, just select points.
 if isKdens==0:
 arcpy.SelectLayerByAttribute_management ("pointslyr", "NEW_SELECTION", "\"asno\" = "+asno+"")
 ##++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 #If KDens map, apply symbology
 else:
 arcpy.ApplySymbologyFromLayer_management(lyr, templateLayer)
 ##++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 ###Zoom to selection
 df.zoomToSelectedFeatures()
 lyrExtent = lyr.getSelectedExtent()
 df.extent = lyrExtent
 ###Export to PDF!!!
 ##++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 if isKdens:
 arcpy.mapping.ExportToPDF(mxd, r"F:\\testFiles\\output\\AS_"+asno+"_KDens_Map.pdf")
 ##++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 else:
 arcpy.mapping.ExportToPDF(mxd, r"F:\\testFiles\\output\\AS_"+asno+"_Map.pdf")
except:
 print arcpy.GetMessages()
#####DELETION
del mxd, df, lyrFile, lyrExtent, lyr
print "DELETED MXD AND DFS"

EDIT 2 So, I also tried turning off logging, since I have heard that can cause memory leaks, too. There is still something leaking. I also tried using Delete_management instead of del, but that just messes things up. It almost seems like my code is not running sequentially. A delete after a reference still gives a "references before defined" error...

Anyway, now I am trying to locate the memory leak using memory analyzer packages. Out of all of them that work with Python, I only got objgraph to work. I placed a objgraph.show_growth call before and after the function whose code is above. Here are the results:

Before

tuple 11959 +11959
function 3643 +3643
dict 1632 +1632
wrapper_descriptor 1086 +1086
cell 927 +927
list 635 +635
builtin_function_or_method 590 +590
property 551 +551
method_descriptor 390 +390
weakref 373 +373

After

weakref 398 +25
wrapper_descriptor 1105 +19
tuple 11977 +18
dict 1644 +12
member_descriptor 172 +4
getset_descriptor 213 +3
method_descriptor 392 +2
instance 15 +2
list 636 +1
`_RLock 2 +1

It doesn't look like any of my objects are leaking, though I am not quite sure what instance means in the second growth dump. Anyone have any insights?

• Aaron: Maybe you could post some pseudocode?
• PolyGeo: Are you creating lots of MapDocument objects and not cleaning them up as you go by using del?
• om_henners: Also, where is the output of the kernel density going?
• JamesS: I have no experience of ArcPy, but some of the geoprocessing tools in earlier versions of ArcGIS do leak memory. Python does have garbage collection and, in my experience, memory leaks in ArcGIS scripts are rarely due to Python itself; they're either due to programmer error or to leaky geoprocessing tools. Some options for profiling memory consumption in your Python code are described here
• N-C: @PolyGeo I have updated my original post to answer your question (as well as om_henners') and to provide a bit more information about my code.

Answer 1

Just use the Delete tool. Call arcpy.management.Delete("rdlayer") after saving the layer file.

• N-C: Thanks. I added this after saving the layer file, but python.exe still crashes. There must be some other leak elsewhere, but at least I took care of one of them!
• GeoStoneMarten: export a pdf 2 times with the same mxd without arcpy block my arcmap. It maybe the same problem. I solution it by closing mxd and reopen