[GIS] Download data via a ftp server using polygon features

arcgis-desktoparcpydownloadftppython

The attached script loops through the features of a polygon featureclass and uses that attribute information to download particular files via a ftp server. The script works great for downloading files as long as all of the files on the ftp server are contained within one folder (example).

Now, I need to download imagery via a ftp server with a different file structure (example) where files are contained within multiple folders. How can I tweak the code so that the following actions occur?:

  1. Use polygon features to identify the necessary file to download (completed)
  2. Access the correct folder and download the imagery

I suspect that I need to utilize the os.path module, however, I cannot seem to put the pieces together.

# Download data via a ftp server

import arcpy, ftplib, os, socket

HOST = 'ftp.agrc.utah.gov'
DIRN = '/Imagery/NAIP2011_4-band/'
#FILE = ''     # Defined later in for loop
workspace = r'F:\my\workspace'  # This is where the downloads go
quads = r'F:\path\to\polygon\shapefile' # Used to define which files to download

# Get current working directory
print 'The current working directory is %s' % os.getcwd()

# Change the current working directory to a download folder
os.chdir(workspace)
print 'The workspace has been changed to %s' % workspace 

try:
    f = ftplib.FTP(HOST)
except (socket.error, socket.gaierror), e:
    print 'ERROR: cannot reach "%s"' % HOST
print '*** Connected to host "%s"' % HOST

try:     
    f.login()
except ftplib.error_perm:
    print 'Error: cannot login anonymously'
    f.quit()
print '*** Logged in as "anonymous"'

try:
    f.cwd(DIRN)
except ftplib.error_perm:
    print 'ERROR: cannot CD to "%s"' % DIRN
    f.quit()
print '*** Changed to "%s" folder' % DIRN

# Use search cursor to loop through download polygons,
# get the name of the required file and use that name to download file on ftp site
with arcpy.da.SearchCursor(quads, ("TILE_NAME", "QUADID")) as cursor:
    for row in cursor:
        print row[0]
        FILE = row[0] + ".tif"
        name = row[1]

        try:
            f.retrbinary('RETR %s' % FILE, open(FILE, 'wb').write)
            arcpy.Rename_management(os.path.join(workspace, FILE), os.path.join(workspace, name + ".tif"))
        except ftplib.error_perm:
            print 'ERROR: cannot read file "%s"' % FILE
            os.unlink(FILE)
        else:
            print '*** Downloaded "%s" to CWD' % FILE
f.quit()

Best Answer

In your example you have a root folder containing many numbered folders.

Can you simply:

1) Use python to list the numbered folders:

    files = ftp.dir()
    print files

2) Match your polygon feature to the correct folder

3) Open the correct directory

ftp.cwd("/numbered_folder")

4) Use your existing code to download the files.

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