I am very new at Python,I'm not sure if this is even the appropriate way to do what I want to do, but basically, I'm looking to eliminate all of the small polygons in a feature class that was created to show all of the watershed basins of an area. I will need to run the Eliminate tool multiple times to eliminate all polygons smaller than an acre (since sometimes the tool will combine 2 small polygons and they still end up being less than an acre). Right now I can run the eliminate tool once with:

arcpy.management.SelectLayerByAttribute(basinLYR,"NEW_SELECTION","Acres < 1")

Since I've never used a loop in Python before, I'm not sure which to use or where to place it.


A simple loop for a set number of iterations would look like this:

arcpy.env.overwriteOutput = True #make sure you can overwrite the eliminate output
arcpy.SelectLayerByAttribute_management(basinLYR,"NEW_SELECTION","Acres < 1") 
elim = arcpy.Eliminate_management(basinLYR,basin_elim)
iter = 5 #number of iterations -- how many times to go through the loop

for i in range(iter):
    arcpy.SelectLayerByAttribute_management(elimLYR,"NEW_SELECTION","Acres < 1") 
    elim = arcpy.Eliminate_management(elimLYR,'_'.join([basin_elim,str(i)]))
  • This will just run eliminate on basinLYR 5 times. You need to feed the output of eliminate to the input of the next loop. – Marc Pfister Dec 3 '18 at 19:53
  • FIxed - elim now feeds back into the loop. Thanks for the feedback – jbalk Dec 3 '18 at 20:13
  • A while loop might be better here - 'while number of features selected under criteria x is >0, keep running the tool' – obrl_soil Dec 4 '18 at 0:39
  • When I try the above mentioned I receive the error: "ERROR 000670: output Output Feature Class is same as input Input Layer. Failed to execute (Eliminate)." The error is referring to the last line of code. Any suggestions? – Stan Dec 7 '18 at 15:03
  • If you're using a gdb try my edit above. You need to change the name of the elim layer each time so you're not trying to overwrite it in place. – jbalk Dec 7 '18 at 16:27

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