Using erase tool in Python?

Question

I am trying to create a python scrip to batch erase shapefiles. I have created a script that works, however, I know there is a better way and I just am not good enough at scripting to figure it out. I want to create a loop to allow the script to just to go through the folders and just erase the new shapefile from the old to see change. The way I have it now I have to update about 16 path names. Also, the the script will send me an error if there is nothing to erase. I know this requires an if statement but again, I am just now knowledgeable enough to figure it out. Below, is the scrip that works and hopefully it will give and idea of what it is I am trying to achieve.

import arcpy
#Set workspace
arcpy.env.workspace = "USER_TEMP\\RAY\\test\\"

#Erase workspace
erase_ADE01 = "\\ADE01_ALL_BUFFERS_05_09_16.shp"
erase_COF01 = "\\COF01_ALL_BUFFERS_05_09_16.shp"
erase_CVI04 = "\\CVI04_ALL_BUFFERS_05_09_16.shp"

#Current buffers workspace
current_ADE01 = "\\ADE01_ALL_BUFFERS_TEST.shp"
current_COF01 = "\\COF01_ALL_BUFFERS_TEST.shp"
current_CVI04 = "\\CVI04_ALL_BUFFERS_TEST.shp"

#Outputworkspace
output = "\\test\\delta_test\\"

#Erase tool; NEED HELP-WHEN THERE IS NOTHING TO ERASE SCRIPT FAILS 
arcpy.ET_GPErase(current_ADE01, erase_ADE01, output + "ADE01_ALL_DELTAS_TEST.shp", 0.0)
arcpy.ET_GPErase(current_COF01, erase_COF01, output + "COF01_ALL_DELTAS_TEST.shp", 0.0)
arcpy.ET_GPErase(current_CVI04, erase_CVI04, output + "CVI04_ALL_DELTAS_TEST.shp", 0.0)

print "Script completed"

UPDATE:

So, I don't know why I didn't think of this before but what I did was merge the erase features together so that way there is only one feature to erase from. Then I just threw it in a "for loop" and everything works well for that part. Now I am still getting that error for when there is nothing to erase (the features are the same). How would I write an if statement for this:

#Erase tool; NEED HEELP-WHEN THERE IS NOTHING TO ERASE SCRIPT FAILS
for fc in arcpy.ListFeatureClasses():
   erase_feature =  "\\all_erase.shp" #this is the merged feature
   erase_output = "\\test\\delta_test\\" + "_ALL_DELTAS_TEST.shp"
   arcpy.ET_GPErase(fc, erase_feature, erase_output, 0.0)

UPDATE2:

So, I am getting closer to figuring this out. My script will run all the way to the end now. However, it wasn't erasing because of memory issues. So i upgraded to python64x. Here is my script:

for fc in arcpy.ListFeatureClasses():
prefix = fc[:6] 
erase_output = "\\test\\delta_test\\" + prefix + "_ALL_DELTAS_TEST.shp"
try:
    arcpy.ET_GPErase(fc, merge_output, erase_output, 0.0)
except arcpy.ExecuteError:
    print arcpy.GetMessages(2)
    print "Erase for " + prefix + " unsuccessful"
except:
    print "There has been a non-tool error"

The "There has been a non-tool error" print pops up now that I have downloaded the different pywin. Before I did that, the error was in the first except because of the memory issues. What am I doing wrong?

Answer 1

To avoid reapeating the ET_GPErase tool you can group all of your inputs and outputs in a list, and then use a loop. Here's how that could be achieved:

import arcpy
#Set workspace
arcpy.env.workspace = "USER_TEMP\\RAY\\test\\"

#Erase and Current buffer workspace
eraseAndCurrent = [
    ["/ADE01_ALL_BUFFERS_05_09_16.shp","/ADE01_ALL_BUFFERS_TEST.shp"],
    ["/COF01_ALL_BUFFERS_05_09_16.shp","/COF01_ALL_BUFFERS_TEST.shp"],
    ["/CVI04_ALL_BUFFERS_05_09_16.shp", "/CVI04_ALL_BUFFERS_TEST.shp"]
]


#Outputworkspace
output = "/test/delta_test"

#Erase tool; NEED HELP-WHEN THERE IS NOTHING TO ERASE SCRIPT FAILS
for item in eraseAndCurrent:
    erase = item[0]
    current = item[1]
    prefix = item[0][:6] # assuming that these always have the same length!
    print output + prefix + "_ALL_DELTAS_TEST.shp"
    arcpy.ET_GPErase(current, erase, output + prefix + "_ALL_DELTAS_TEST.shp", 0.0)


print "Script completed"