topic Re: Union all shapefiles in a geodatabase in Python Questions

Union all shapefiles in a geodatabase

SuyunMa — Thu, 02 Aug 2012 18:04:07 GMT

Hi,
I have 2806 polygon shapefiles stored in the same geodatabase and I want to union all of them together. So I was wondering how can I do that by using Python script. Thanks a lot.

SYM

Re: Union all shapefiles in a geodatabase

JakeSkinner — Sat, 11 Dec 2021 06:27:56 GMT

Hi SYM,

Here's an example:

import arcpy
from arcpy import env
env.workspace = r"C:\temp\python\test.gdb"

lstFCs = arcpy.ListFeatureClasses("*", "POLYGON")
arcpy.Union_analysis(lstFCs, "Union_FC")

This script is creating a list of all the polygon feature classes, and then passing this list as the input for the Union GP tool.

Re: Union all shapefiles in a geodatabase

SuyunMa — Sat, 11 Dec 2021 06:27:58 GMT

Thanks a lot.

Hi SYM,

Here's an example:
import arcpy
from arcpy import env
env.workspace = r"C:\temp\python\test.gdb"

lstFCs = arcpy.ListFeatureClasses("*", "POLYGON")
arcpy.Union_analysis(lstFCs, "Union_FC")
This script is creating a list of all the polygon feature classes, and then passing this list as the input for the Union GP tool.

Re: Union all shapefiles in a geodatabase

ChristopherThompson — Wed, 22 Aug 2012 18:48:08 GMT

Does ArcView allow more than two inputs to a union? I think that AV only accepts two inputs for intersects and think the same limitation applies to other overlay processes like union.

Re: Union all shapefiles in a geodatabase

ChrisSnyder — Sat, 11 Dec 2021 06:28:01 GMT

ArcView only allows two FCs to be unioned at a time. Here is some ***untested*** Python code that could serve as a work-around:

#Be carefull to delete any "tmp_*" or "final_union" FCs before you run the code... otherwise those'll get unioned too
import arcpy
arcpy.env.workspace = r"C:\temp\python\test.gdb"
fcList = arcpy.ListFeatureClasses("*", "POLYGON")
i = 0
for fc in fcList:
   i = i + 1
   if i == 1:
      unionFcList = [fcList[i-1],fcList]
   else:
      inputTmpFC = "tmp_" + str(i-1)
      unionFcList = [fcList,inputTmpFC]
   outTmpFC = "tmp_" + str(i)
   arcpy.Union_analysis(unionFcList, outTmpFC)
   arcpy.Delete_managment(inputTmpFC)
arcpy.Rename_managment(outTmpFC, "final_union")