topic Re: Loop a function over all files in a folder with Python and GIS in Python Questions

Loop a function over all files in a folder with Python and GIS

FrédéricLeTourneux — Fri, 10 Dec 2021 22:11:39 GMT

Hi,

I am new to python and I'm trying to use the python interface in ArcGIS to loop a function (buffer) over all files in a directory that I specified. I come up with the script below. However, when I run it, no errors are returned, but no files are created, nothing happens. What do I do?

 #Import arcpy
import arcpy
import os

#Naming the directory
rootdir = "C:\\Users\\Fred\\Desktop\\GIS\\ModelBuilder Project\\TEST"

#allowing overwriting
arcpy.env.overwriteOutput = True

#Setting up counter
thectr = 0

#For-loop for looping function over all files in a folder
for subdirs, dirs, files in os.walk(rootdir):

    for file in files:
        if file == '*.shp':
# Variables
            input_layer = files
            output_layer = "C:\\Users\\Fred\\Desktop\\GIS\\ModelBuilder Project\\TEST\\test" + str(thectr)
# Process: Buffer
            arcpy.Buffer_analysis(input_layer, output_layer, "1 Kilometers", "FULL", "ROUND", "ALL", "")
#Update counter
            thectr=thectr+1

I've also tried the script below, with the same result:

# import modules
import arcpy, glob

# folder where shapefiles are stored
folder = 'C:/myfiles/'

# loop through all shapefiles
for shapefile in glob.glob( folder + '*.shp' ):
     arcpy.Buffer_analysis( shapefile, "C:/output/" + shapefile[-8:-4] + "buffer.shp" "100 Feet", "FULL", "ROUND", "LIST", "Distance")

Ideas?

Re: Loop a function over all files in a folder with Python and GIS

GerryGabrisch — Fri, 13 Feb 2015 00:30:17 GMT

The output file name needs a '.shp' maybe?

output_layer = "C:\\Users\\Fred\\Desktop\\GIS\\ModelBuilder Project\\TEST\\test" + str(thectr) +".shp"

Re: Loop a function over all files in a folder with Python and GIS

FrédéricLeTourneux — Fri, 13 Feb 2015 00:42:05 GMT

Still not working =/

Thanks though.

Re: Loop a function over all files in a folder with Python and GIS

DarrenWiens2 — Fri, 13 Feb 2015 01:12:09 GMT

In your second script (the glob script), what is the output of "print shapefile' inside the loop? Does it list anything? If so, do you notice anything out of the ordinary?

Re: Loop a function over all files in a folder with Python and GIS

Zeke — Fri, 10 Dec 2021 22:11:42 GMT

You're setting input_layer to files. files is a list, not a shapefile or layer.

Also, don't think 'if file = '*.shp' will work. The * isn't working as a wildcard in this case, so most likely you're never entering the if block. This is also indicated by the fact that no error is being thrown. That code is never run.

You could try: if file.endswith('.shp) instead. Or import fname and use: if fname.fname('*.shp').

I'd also suggest putting in some print statements so you can see what values you're getting and where in the code you are.

#For-loop for looping function over all files in a folder  
for file in files:  
    if file.endswith('.shp'):  
        print('File name is: {0}'.format(file)
    # Variables  
        output_layer = "C:\\Users\\Fred\\Desktop\\GIS\\ModelBuilder Project\\TEST\\test" + str(thectr)  
        arcpy.Buffer_analysis(file, output_layer, "1 Kilometers", "FULL", "ROUND", "ALL", "")

Re: Loop a function over all files in a folder with Python and GIS

DarrenWiens2 — Fri, 10 Dec 2021 22:11:45 GMT

This embellishment on your second (glob) script works for me. It saves the shapefile with the same name to a test folder. You can easily add a suffix, if you want:

>>> import glob, os
>>> folder = r'C:/junk/'
>>> for shapefile in glob.glob( folder + '*.shp' ):
...     output = os.path.join(r'C:/junk/test' + os.path.basename(shapefile))
...     arcpy.Buffer_analysis( shapefile, output, '100 METERS')

Re: Loop a function over all files in a folder with Python and GIS

FC_Basson — Fri, 10 Dec 2021 22:11:48 GMT

A combo of Greg's and Darren's answer worked for me:

import arcpy, os, string
rootFolder = 'C:\\test'
ctr = 1
for root, dirs, files in os.walk(rootFolder):
   for name in files:      
      if name.endswith(".shp"):
         # shapefile name without extension
         shpName = os.path.splitext(name)[0]
         # absolute file path
         absFile = os.path.abspath(os.path.join(root,name))     
         # output file path    
         output_layer = rootFolder + '\\buffer_' + shpName + '_' + str(ctr) + '.shp'         
         # buffer
         arcpy.Buffer_analysis(absFile, output_layer, "1 Kilometers", "FULL", "ROUND", "ALL", "") 
         ctr = ctr + 1

Re: Loop a function over all files in a folder with Python and GIS

BlakeTerhune — Tue, 17 Feb 2015 18:39:44 GMT

Just for funzies, if you are using a simple counter like you do at the end with ctr, you can also use += 1 to make the code a little simpler. Just know that += might not always be what you want.

ctr += 1

Re: Loop a function over all files in a folder with Python and GIS

RichardKammer — Fri, 10 Dec 2021 22:11:51 GMT

I would try the arcpy.ListFeatureClasses() to get a list of shape file in folder.

import os
import arcpy

# Set the workspace for ListFeatureClasses
dirpath = "C:/Users/Fred/Desktop/GIS/ModelBuilder Project/TEST"
arcpy.env.workspace = dirpath
# Use the ListFeatureClasses function to return a list of shapefiles.
featureclasses = arcpy.ListFeatureClasses()
# loop through the list of shape files
for ifc in featureclasses:
 ofc = os.path.join(dirpath,os.path.splitext(ifc)[0] + "_Buffer.shp")
    arcpy.Buffer_analysis(ifc,ofc,"1 Kilometer","FULL","ROUND","ALL","")

Re: Loop a function over all files in a folder with Python and GIS

Hernando_CountyProperty_Apprai — Thu, 19 Feb 2015 18:25:09 GMT

I'm doing the same type of thing except with an append. I pass in the folder as an argument.

# Get list of shape files from specified directory

path = sys.argv[1] + "\\*.shp"

directory = glob.glob(path)

for filename in directory:

try:

arcpy.Append_management(filename,sys.argv[4], "NO_TEST", "SHAPE.AREA \"SHAPE.AREA\" false false true 0 Double 0 0 ,First,#;SHAPE.LEN \"SHAPE.LEN\" false false true 0 Double 0 0 ,First,#", "")

except:

arcpy.AddMessage(traceback.format_exc())

error = "Y"

Re: Loop a function over all files in a folder with Python and GIS

ToddBlanchette — Fri, 20 Feb 2015 01:17:28 GMT

Since you're trying to list feature classes within a workspace (in your example: shapefiles in a directory) why not stick with arcpy instead of trying to manipulate all the string possibilities? Arcpy.ListFeatureClasses() method will give you all the shapefiles you're looking to buffer and just set the environment to the working directory. This will also help if you move to geodatabases, as windows directory structure won't work to get you your feature classes in there.

Hope this helps,

Todd