topic Re: Need help building my first script in Python Questions

Need help building my first script

AntoineCantin — Mon, 28 Mar 2016 16:19:36 GMT

Hi, I'm trying to build a script, my first, so that it would create another version of some polygons in a shapefile (per example zoning)by erasing some polygons contained in a different shapefile (called hydro). I don't have a Pro license, so I use the "Union then delete" method instead of the erase tool. I don't want the attributes from the hydro table. I want to duplicate the script to apply those modification to other shapefiles. So here is what I found for the moment:

# Import the system modules

import arcpy

from arcpy import env

# Set the current workspace

# (to avoid having to specify the full path to the feature classes each time)

env.workspace = "c:/data/data.gdb"

# For first layer

#Turn off all fields of hydro.shp so when union is done, the attributes table will only keep the fields from "zoning", leaving out the turned off fields of "hydro"

#Can't find script lines for that

#union layerName with hydro.shp

#Source: http://help.arcgis.com/En/Arcgisdesktop/10.0/Help/index.html#//00080000000s000000

arcpy.Union_analysis (["layerName", "hydro", "layerName_union", "ALL")

#select FID_hydro <> -1

#Source: http://help.arcgis.com/En/Arcgisdesktop/10.0/Help/index.html#//001700000071000000)

arcpy.SelectLayerByAttribute_management ("layerName_union", "NEW_SELECTION", " [FID_hydro] <> '-1' ")

#If selection > 0, delete FID_hydro <> -1

#Source: http://help.arcgis.com/EN/ARCGISDESKTOP/10.0/HELP/index.html#//001700000036000000

if int(arcpy.GetCount_management(layerName_union).getOutput(0)) > 0:

arcpy.DeleteFeatures_management(layerName_union)

#export data layerName_union as shapefile

#Source: http://resources.arcgis.com/en/help/main/10.1/index.html#//001200000020000000

arcpy.FeatureClassToFeatureClass_conversion("layerName_union","C:/Chemin/vers/dossier","layerName_noHydro.shp")

# Repeat for other layers

Anyone know how to use script to turn off all the field of a layer?

Would those steps work? Is there something missing?

Thanks,

Re: Need help building my first script

DarrenWiens2 — Mon, 28 Mar 2016 16:42:10 GMT

I think you're looking for the Delete Field tool.

If you need more help, please include your code within code tags so we can copy/paste/more easily read. Posting Code blocks in the new GeoNet

Re: Need help building my first script

DanPatterson_Retired — Mon, 28 Mar 2016 16:43:50 GMT

and featureclasstofeatureclass allows you to remove fields during the fieldmapping process Feature Class to Feature Class—Help | ArcGIS for Desktop

Re: Need help building my first script

AdrianWelsh — Mon, 28 Mar 2016 17:18:48 GMT

Hi Antoine,

To reiterate what others said, consider using the code block in the forum post:

use Advanced Editor in the thread and click on the double arrows, go to syntax then Python:

I like the commenting you have done in your code, it helps for others to see. Have you tried running your code to see if it works? You may want to how you format your path strings. There are many different ways to do this, here are some examples:

In your DeleteFeatures_Management, you do not have quotes around your layer name. From looking at other lines of code in your block, you will need those quotes.

Re: Need help building my first script

AntoineCantin — Sat, 11 Dec 2021 20:13:14 GMT

# Import the system modules
import arcpy
from arcpy import env

# Set the current workspace
# (to avoid having to specify the full path to the feature classes each time)
env.workspace = "c:/data/data.gdb"

# For first layer
#Copy hydro.shp and delete all field of hydro_copy.shp so when union is done, the attributes table will only keep the fields from "zoning", leaving out the turned off fields of "hydro 
arcpy.opyFeatures_management("hydro.shp", "C:/output/hydro_copy.shp")
arcpy.DeleteField_management("C:/output/hydro_copy.shp",["STREET_NAM", "LABEL", "CLASS"])

 #union layerName with hydro.shp
acpy.Union_analysis (["layerName", "hydro", "layerName_union", "ALL")

#select FID_hydro <> -1
arcpy.SelectLayerByAttribute_management ("layerName_union", "NEW_SELECTION", " [FID_hydro] <> '-1' ")
#If selection > 0, delete FID_hydro <> -1
 if int(arcpy.GetCount_management(layerName_union).getOutput(0)) > 0:
arcpy.DeleteFeatures_management(layerName_union)

#export data layerName_union as shapefile
  arcpy.FeatureClassToFeatureClass_conversion("layerName_union","C:/Chemin/vers/dossier","layerName_noHydro.shp")

#ReaRepeat for other layers
#Repeat for other layers

Is this better? Maybe it's my Chrome browser but the editor isn't friendly to use.

Re: Need help building my first script

AntoineCantin — Mon, 28 Mar 2016 19:25:29 GMT

Would it looks like that?

arcpy.FeatureClassToFeatureClass_conversion("Affectations_Union","C:\Users\Antoine\Desktop\test","layerName_shape.shp",,removeAll ())

Re: Need help building my first script

DanPatterson_Retired — Mon, 28 Mar 2016 20:23:00 GMT

according to this FieldMappings—Help | ArcGIS for Desktop in scripting, I think that would be correct, but I am not at a machine to test at present

Re: Need help building my first script

AntoineCantin — Mon, 28 Mar 2016 20:38:37 GMT

Don't seem to work, I get this message:

"Parsing error SyntaxError: invalid syntax (line 1)" !?

Re: Need help building my first script

DanPatterson_Retired — Mon, 28 Mar 2016 20:51:01 GMT

fms = arcpy.FieldMappings()

fms.removeAll()

Create the output feature class, using the FieldMappings object arcpy.FeatureClassToFeatureClass_conversion( in_file, arcpy.env.workspace, out_file, field_mapping=fms)

guess-ta-coding from the help files

Re: Need help building my first script

DanPatterson_Retired — Mon, 28 Mar 2016 20:53:22 GMT

or you can't have ,, in a row, something has to be inbetween

Re: Need help building my first script

AdrianWelsh — Mon, 28 Mar 2016 20:54:48 GMT

Antoine, there are a few typo errors in your code that you have posted (just briefly glancing through this, I see "opyFeatures_management" which is missing the letter "c". Also, for your path strings, you should put an "r" in front of the path to make it the raw path:

r"C:\Users\Antoine\Desktop\test"

since it is reading it differently (looking at the "\t", etc.)

What python editor are you using? You might consider something like PyCharm or PyScripter (both free) that will find errors like this and give suggestions.

Re: Need help building my first script

AntoineCantin — Sat, 11 Dec 2021 20:13:17 GMT

I tried this:

fms = arcpy.FieldMappings()
fms.removeAll()
arcpy.FeatureClassToFeatureClass_conversion("Lac","C:/Users/Antoine/Desktop/test","Lac_empty.shp","fms")

I get this message now:

"Runtime error Traceback (most recent call last): File "<string>", line 1, in <module> File "c:\program files (x86)\arcgis\desktop10.2\arcpy\arcpy\conversion.py", line 1685, in FeatureClassToFeatureClass raise e ExecuteError: ERROR 999999: Error executing function. An invalid SQL statement was used. An invalid SQL statement was used. Failed to execute (FeatureClassToFeatureClass). "

When I try to use the FeatureClassToFeatureClass tool, in the UI, I get another error message. I tried to solve it with this solution. Still not working.

Re: Need help building my first script

AntoineCantin — Mon, 28 Mar 2016 21:42:35 GMT

Thanks! I corrected it and just downloaded PyCharm

Re: Need help building my first script

DanPatterson_Retired — Mon, 28 Mar 2016 22:15:02 GMT

the syntax I posted was field_mapping=fms)

You assigned it a text value "fms" which will surely fail. Check the exact syntax in the help files and what the defaults are if you omit parameters. You can't just omit parameters by using ,, or changing object properties ( a fieldmap is a type of object which is not a string object). These errors aren't caught by IDE's, the clues are in the reported message, unfortunately they are interpreted with respect to the object expected and not by what the user expect to be given to solve the problem.

Re: Need help building my first script

AntoineCantin — Mon, 28 Mar 2016 23:38:05 GMT

I copied the wrong one. I tried yours at first, partly worked. I mean, a layer was saved as a new shape, but had the same fields as the original.

Re: Need help building my first script

curtvprice — Tue, 29 Mar 2016 03:46:36 GMT

This is because it was an empty fms object, so it used the default - which is a complete field map that keeps all the fields.

Re: Need help building my first script

DanPatterson_Retired — Sat, 11 Dec 2021 20:13:20 GMT

@ Antoine Cantin on 28-Mar-2016 4:51 PM

Mark Correct

Correct Answer

ahhh perhaps...

fm = arcpy.FieldMap()

fms = arcpy.FieldMappings() 
fms.removeAll()
fm.outputField = "out_stuff"
fms.addFieldMap(fm)
 #Create the output feature class, using the FieldMappings object 
arcpy.FeatureClassToFeatureClass_conversion( in_file, arcpy.env.workspace, out_file, field_mapping=fms)

might work but I would have to try it though... parsed from 2nd example here

FieldMappings—Help | ArcGIS for Desktop

Re: Need help building my first script

AntoineCantin — Tue, 29 Mar 2016 13:59:20 GMT

When I try it exactly like you posted I get an error message, but my guess is that I'm doing something wrong... What is the fm.outputField? Should I replace "out_stuff" by something?

Re: Need help building my first script

DanPatterson_Retired — Tue, 29 Mar 2016 20:38:43 GMT

the field map output field... and it would be the name of the field you want to output... the example in the help topic seems reasonable, however, it might be best to go with Darren's deleting multiple fields... and providing all their names, or excluding the one you want to keep, ... than providing the name of the field or fields you want to keep.

Re: Need help building my first script

DarrenWiens2 — Tue, 29 Mar 2016 20:48:24 GMT

As a lazy coder, I would only use FieldMap and FieldMappings as a last resort. They are complete outliers in the context of arcpy.