topic Re: ERROR 000871 or Schema Lock Trying to write over shapefiles in iteration. in Python Questions

ERROR 000871 or Schema Lock Trying to write over shapefiles in iteration. UPDATE

AndyLaney — Sun, 11 Jul 2021 06:55:04 GMT

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Forgive me, my language is probably off - I'm very new to programming and this is the first real script I've been asked to write. It's simple, runs through some geoprocessing tools and then prints out a map. When I run it outside of a loop it works fine, however when I get to the point in the second iteration where a mask is extracted from an RGB image file it fails, this is the error I get:

File "C:/Iteration.py", line 34, in <module>
APN8_Raster.save(Extract_by_Mask)
RuntimeError: ERROR 000871: Output Raster: Unable to delete the output C:\Extract_RSF.

I've also gotten a schema lock error, my worry is that the shapefiles I'm looking to overwrite are locked for some reason. I run this script through PyCharm - ArcGIS Pro is closed so for the life of me I cannot figure out why it locks or why it cannot be overwritten. I believe it will do the same thing with the other 2 shape-files required in the process that need to be overwritten in every iteration.

Here's the code:

import arcpy from arcpy import env env.workspace = r"C:\Users\nahgl\Firewatch\Firewatch.gdb" env.overwriteOutput = True fc = "Parcels" field = ["APN_8"] RGB_of_RSF = arcpy.Raster("RSF_RGBe_FW2020") Parcels = "Parcels" Buildings = "Buildings" SQL_Expression = "APN_8 = '26603028'" Map_Expression = "OBJECTID = 1" Symbology50 = r"C:\Users\nahgl\Firewatch\Python\Symbology_50.lyrx" Symbology100 = r"C:\Users\nahgl\Firewatch\Python\Symbology_100.lyrx" with arcpy.da.SearchCursor(fc, field) as cursor: for row in cursor: print(row[0]) APN = "APN_8 = " + "'" + row[0] + "'" # Process: Select Parcel (Select) (analysis) Selected_Parcel = r"C:\Users\nahgl\Firewatch\Firewatch.gdb\Parcels_Select" arcpy.analysis.Select(in_features=Parcels, out_feature_class=Selected_Parcel, where_clause=APN) # Process: Select Building (Select) (analysis) Selected_Buildings = r"C:\Users\nahgl\Firewatch\Firewatch.gdb\Buildings_Select" arcpy.analysis.Select(in_features=Buildings, out_feature_class=Selected_Buildings, where_clause=APN) # Process: Extract by Mask (Extract by Mask) (sa) APN8_Raster = r"memory\Extract_RSF" Extract_by_Mask = APN8_Raster APN8_Raster = arcpy.sa.ExtractByMask(in_raster=RGB_of_RSF, in_mask_data=Selected_Parcel) APN8_Raster.save(Extract_by_Mask) # Process: Buffer 100 (Buffer) (analysis) Buffer_Output_100 = r"memory\Buffer_100" arcpy.analysis.Buffer(in_features=Selected_Buildings, out_feature_class=Buffer_Output_100, buffer_distance_or_field="100 Feet", line_side="FULL", line_end_type="ROUND", dissolve_option="ALL", dissolve_field=[], method="PLANAR") # Process: 100ft Buffer Symbology (Apply Symbology From Layer) (management) Buffer_Output_100 = arcpy.management.ApplySymbologyFromLayer(in_layer=Buffer_Output_100, in_symbology_layer=Symbology100, symbology_fields=[], update_symbology="DEFAULT")[0] # Process: Buffer 50 (Buffer) (analysis) Buffer_Output_50 = r"memory\Buffer_50" arcpy.analysis.Buffer(in_features=Selected_Buildings, out_feature_class=Buffer_Output_50, buffer_distance_or_field="50 Feet", line_side="FULL", line_end_type="ROUND", dissolve_option="ALL", dissolve_field=[], method="PLANAR") # Process: 50ft Buffer Symbology (Apply Symbology From Layer) (management) Buffer_Output_50_Final = arcpy.management.ApplySymbologyFromLayer(in_layer=Buffer_Output_50, in_symbology_layer=Symbology50, symbology_fields=[], update_symbology="DEFAULT")[0] # Process: Selecting the Project file = Firewatch & Map = RSF_Parcels project = arcpy.mp.ArcGISProject(r"C:\Users\nahgl\Firewatch\Firewatch.aprx") map = project.listMaps('RSF_Parcels')[0] print(map.name) # Process: Selecting Buffer_100 as Zoom in layer (Or by Parcels) layer = map.listLayers('Buffer_100')[0] print(layer) # layer = map.listLayers('Parcel')[0] ##If Parcel is used as zoom in layer Map_Expression must be changed to SQL_Expression arcpy.SelectLayerByAttribute_management(layer, "NEW_SELECTION", Map_Expression) # Process: Selecting Layout that will be used lyt = project.listLayouts("RSF_Layout")[0] print(lyt.name) # Process: Listing all elements within the layout mf = lyt.listElements('MAPFRAME_ELEMENT', '*')[0] # Process: Setting the extent of the map camera to the selected layer (Buffer_100 or Parcel) & then zooming into frame mf.camera.setExtent(mf.getLayerExtent(layer, True, True)) mf.zoomToAllLayers() # Clear the 100 Buffer Selection so it isn't blue arcpy.management.SelectLayerByAttribute(layer, "CLEAR_SELECTION") # Process: Importing the layout with the zoomed in image to a JPEG (Needs better naming) lyt.exportToJPEG( r"C:\Users\nahgl\Firewatch\scratch\RGB_%s" % APN[9:-1])

I've tried deleting the shapefiles after the image is created, this is where I get the schema lock:

"arcgisscripting.ExecuteError: ERROR 000464: Cannot get exclusive schema lock. Either being edited or in use by another application or service.
Failed to execute (Delete)."

I've done a lot of Google sloothing which leads be to believe this could be a bug? Not sure, using Python 3.7, any advice or help would be much appreciated. Thank you.

Re: ERROR 000871 or Schema Lock Trying to write over shapefiles in iteration.

DanPatterson — Sat, 10 Jul 2021 18:20:56 GMT

you need to put your files into a folder... writing to, and reading from the root folder (C:\) is just asking for trouble.

Also, overwriting files is controlled at the project level in Pro, under Geoprocessing Options or by setting the flag within the script (arcpy.env.overwriteOutputs=True) as you have done. However, if a file is used within a loop it may not be able to be deleted until the whole process is complete.

"C:\Fire.gdb\Fire.gdb\Buildings_Select"

a gdb in a gdb?

Re: ERROR 000871 or Schema Lock Trying to write over shapefiles in iteration.

DavidPike — Sat, 10 Jul 2021 18:38:22 GMT

To be sure of no unintended stuff going on with your paths I'd make sure everything is named with the same raw formatting r'...' as per

project = arcpy.mp.ArcGISProject(r"C:\Fire.aprx")

I think you could avoid a lot of the overrides by using the memory workspace and deleting the memory objects each loop.

I'd follow Dan's suggestions in the first instance.

A final irrelevant point, I've not seen % used in strings very often, I'd say f strings or .format() is preferred.

Re: ERROR 000871 or Schema Lock Trying to write over shapefiles in iteration.

AndyLaney — Sat, 10 Jul 2021 19:21:37 GMT

I removed the middle file paths, sorry for complicating things. Paths are like this:

r"C:\Users\nahgl\OneDrive\Desktop\GIS Project\Firewatch\Firewatch.gdb\Parcels_Select"

Would a pause work before it iterates again to clear the lock?

Re: ERROR 000871 or Schema Lock Trying to write over shapefiles in iteration.

AndyLaney — Sat, 10 Jul 2021 19:26:23 GMT

I was reading up on memory workspaces but not quite getting how to implement it. The extracted mask, buffer_100, and buffer_50 would only exist in memory and then it would erase it after the JPEG is produced?

Re: ERROR 000871 or Schema Lock Trying to write over shapefiles in iteration.

DanPatterson — Sat, 10 Jul 2021 20:15:20 GMT

I would try it at least. It is better than trying to delete things until outputs are derived

Re: ERROR 000871 or Schema Lock Trying to write over shapefiles in iteration.

AndyLaney — Sun, 11 Jul 2021 00:40:02 GMT

What about using the scratch workspace?

Re: ERROR 000871 or Schema Lock Trying to write over shapefiles in iteration.

DanPatterson — Sun, 11 Jul 2021 01:30:49 GMT

Did you try it? Nothing is going to happen to the inputs data if you try stuff in the scratch workspace or in_memory. Either or.. Focus on getting to work, then optimize for speed or convenience after