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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.MakeFeatureLayer(basinFC,basinLYR)
arcpy.management.SelectLayerByAttribute(basinLYR,"NEW_SELECTION","Acres < 1")
arcpy.management.Eliminate(basinLYR,basin_elim)

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

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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.MakeFeatureLayer_management(basinFC,basinLYR) 
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.MakeFeatureLayer_management(elim,elimLYR)
    arcpy.SelectLayerByAttribute_management(elimLYR,"NEW_SELECTION","Acres < 1") 
    elim = arcpy.Eliminate_management(elimLYR,'_'.join([basin_elim,str(i)]))
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  • This will just run eliminate on basinLYR 5 times. You need to feed the output of eliminate to the input of the next loop. Dec 3, 2018 at 19:53
  • FIxed - elim now feeds back into the loop. Thanks for the feedback
    – jbalk
    Dec 3, 2018 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, 2018 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, 2018 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, 2018 at 16:27

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