Is there a script to batch erase the equivalent of a shp to multiple other shps? (in ArcGIS)

Question

I'm looking for a way to be able to frequently update a bunch of shapefiles (different land use and other areas). I would like to erase from them the lakes and rivers which are in another shape (hydro.shp).

I could just do them on by one but it doesn't sound really time effective considering that the hydro.shp is often modified. To add to the problem, I have a basic license, so I can't use the erase tool...

So, how to batch erase without the erase tool?

Answer 1

Here is an updated answer based on a better understanding of your request. This code performs a union between the eraser and the erasee shapefiles and then selects the overlapping features and deletes them .It then deletes the unnecessary fields to maintain just the original fields from the original shapefiles. I clip the hydro layer first just to remove any extraneous features to avoid errors. In the future you could convert this to an arcgis tool so you can feed in the shapefiles as parameters as opposed to hardcoding the paths to the shapefiles. This worked on the sample dataset I had. Let meknow if it works for you.

import arcpy
import os

#delete any data tha might be stored in memory
arcpy.Delete_management("in_memory")

#set workspace to where all your shapefiles are 
arcpy.env.workspace="c:/data"

#define where the hydro shapefile is located, ideally in a different folder than the others 
hydroshp="c:/mydata/hydro.shp"

fcs=arcpy.ListFeatureClasses()
for fc in fcs:
    #create an empty list to be populated with the original shapefile's field names
    fieldnames=[]

    #List all fields in the shapefile and populate the fieldnames list with their names
    fields=arcpy.ListFields(fc)
    for field in fields:
        fieldnames.append(field.name)

    #define layer name for each shapefile
    fclayer=fc.rstrip(".shp")

    #create output files for the clip and the union layers
    fcClip=os.path.join("in_memory",fclayer+"clip")
    fcUnion=fclayer+"union.shp"#os.path.join("in_memory",fclayer+"union")

    #clip the shapefile using the hydro layer
    arcpy.Clip_analysis(fc,hydroshp,fcClip)

    #create a union of the clipped hydro and the shapefile
    arcpy.Union_analysis([fc,fcClip],fcUnion,"ALL")

    #delete any unnecessary fields from your union shapefile
    unionfields=arcpy.ListFields(fcUnion)
    for ufield in unionfields:
        if ufield.name not in fieldnames:
            arcpy.DeleteField_management(fcUnion,ufield.name)

    #Create layer file so you can perform a selection on it
    arcpy.MakeFeatureLayer_management(fcUnion,fclayer)
    arcpy.SelectLayerByLocation_management(fclayer,"WITHIN",fcClip)

    #Check if there are any selected features so you don't accidentally delete all the features.
    desc=arcpy.Describe(fclayer)
    if desc.FIDSet != "":
        arcpy.DeleteFeatures_management(fclayer)    
print "done!!"

Answer 2

Short of a script, you could try this in the meantime.

1) http://www.wwu.edu/huxley/spatial/tut/erase.htm

This web page recommends you

1) Union both polygons

2) Select the Polygons from the Unioned Polygon via select by location where Unioned polygons intersect your erased polygon (Hydro.shp)

3) Begin Editing and Delete Selected polygons from your Unioned Polygon.

Note: this could cause issues if you have a layer that gets selected that you do not want erased.

You can put all of this inside a model in model builder to make it easier for you.

Answer 3

import arcpy
#set workspace to where all your shapefiles are
arcpy.env.workspace="c:/data"
#define where the hydro shapefile is located, ideally in a different folder than the others
hydroshp="c:/mydata/hydro.shp"
fcs=arcpy.ListFeatureClasses()
for fc in fcs:
    #define layer name for each shapefile
    fclayer=fc.rstrip(".shp")
    #Create layer file so you can perform a selection on it
    arcpy.MakeFeatureLayer_management(fc,fclayer)
    arcpy.SelectLayerByLocation_management(fclayer,"ARE_IDENTICAL_TO",hydroshp)
    #Check if there are any selected features so you don't accidentally delete all the features.
    desc=arcpy.Describe(fclayer)
    if desc.FIDSet != "":
        arcpy.DeleteFeatures_management(fclayer)       
print "done!!"