How to list all folders in a ftp directory?

Question

I am trying to list the folders in a ftp directory so that the output is as follows:

[32114, 32115, 32116, ..., 42123]

The following script accesses the ftp site. How can I access the folders in the ftp directory using the attached script as a start?

import arcpy, ftplib, os, socket

HOST = 'atlas.ca.gov'
DIRN = '/pub/naip/2012/doqqs_combined_color-nir/'
workspace = 'F:/download/location'

# 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

Answer 1

Building on the answer by abarnert, the following produces the list:

from ftplib import FTP
ftp = FTP('atlas.ca.gov')
ftp.login()
ftp.cwd('/pub/naip/2012/doqqs_combined_color-nir/')
print ftp.nlst()

Answer 2

If you look at the ftplib docs, there are two obvious functions for this: nlst and dir.

Either one will give you a list of all members in the directory, both files and subdirectories.

With nlst, you don't get any information beyond the name. But if you were planning to chdir or otherwise use each one of them, that's OK; you will get exceptions for the ones that turned out to be regular file, and can just skip over them.

With dir, you get a full directory listing, in human-readable form. Which you will have to capture (by passing a callback function) and then parse manually—which is a lot less fun, but the only way you can know in advance which members are files and which are directories.

Answer 3

If the server is a windows machine, the output of ftp.dir() will look like 01-14-14 04:21PM <DIR> Output

If the server is of the *nix variety, the output will look like drwx------ 3 user group 512 Apr 22 2005 Mail

If you want to check if an item is a directory, use a regular expression on each line. Windows FTP server will contain <DIR> if the item is a directory and *nix ftp servers will start with d.

Do you need help with Python regexes?