Python Toolbox - ArcGIS Pro layer locked after subsequent runs - what is stored in "memory"?

[I_AM_ERROR]

I have a python toolbox that is performing various operations on a layout. Reconfigure text elements, pan the map frame, export to PDF being the core functionality. Editing data is not involved.

The tool runs fine initially, but after trying a second run one of the map layers is "locked" in the layout which is causing various issues with tool execution.

My question is: Is Pro keeping variables, objects, classes, etc. in memory between tool runs? If so, how do I clear this so each tool run is new? Is the python process left running once the toolbox is opened?

Additional details:

• closing Pro and running the tool again remedies the issue - lock is only applied after second run
• Used del() to remove object and variables followed by gc.collect() at the end of the toolbox code execute to no avail
• my IDE is VS Code - running here using the approach mentioned here does not present the issue, assuming this is due to each run being a distinct process run and closure, with nothing mainted in between

[DanPatterson]

If it is created and added to in memory, then you can use

Delete (Data Management)—ArcGIS Pro | Documentation

del and gc won't occur until the script/tool is done.

Also, if something is being created, you can use the "overwriteOutput" environment variable

[Anonymous User]

According to the mapping docs: 

When you use the CURRENT keyword in the Python window with ArcGIS Desktop, you sometimes had to call refreshActiveView to force a screen refresh. This is no longer the case with ArcGIS Pro. All arcpy.mp API changes directly update ArcGIS Pro.

 I haven't tried this yet in Pro, but maybe something like 

aprx = arcpy.mp.ArcGISProject("CURRENT")
aprx.save()

at the end of your code to force the changes?

[DonMorrison1]

I'm quite sure a new process is not started to run a toolbox tool, so yes, python is keeping things in memory - specially those created at the toolbox/tool class level and even in the getParameterInfo method. I've found number of places where locks are left dangling (even reported some with no resolution) and can't find a way around them other than to restart ArcGIS Pro (or restart the python kernel if running in the IDE) - good luck with this one!

[I_AM_ERROR]

I think I traced it down something being done in the update parameters method which I can't debug in IDE, either:

• arcpy.SelectLayerByAttribute_management
• arcpy.ListFields
• or arcpy.da.SearchCursor (used via list comprehension)

my guess is the cursor is being left open when used via list comprehension. 

obligatory - "code was inherited from someone else!"

[DanPatterson]

SearchCursor—ArcGIS Pro | Documentation

use the "with" syntax for cursors...

Search cursors also support with statements to reset iteration and aid in removal of locks. 

[Anonymous User]

my guess is the cursor is being left open when used via list comprehension. 

That could be an important detail - cursors are usually called using `with` to ensure the entry and exit get hit. Perhaps it's dangling if not closed properly? Curious to see if that caused it.

[I_AM_ERROR]

It was - well, it's currently commented out and execution is running and not leaving layer locks in the map anymore. If I re-enable I'll use "with" and report back.