newbie question About O'Reilly "Python for Unix and Linux SystemAdministration" ftp Mirror question

Discussion in 'Python' started by moonhkt, Sep 16, 2012.

  1. moonhkt

    moonhkt Guest

    Hi All

    O'Reilly Book ISBN 978-986-6840-36-4.

    python --version
    Python 2.6.2 on AIX 5.3

    Using this python to get files in ftp server.

    I got below error. What is the error meaning and how to fix ?
    Traceback (most recent call last):
    File "/xx../shell/", line 80, in <module>
    f = FTPSync(, options.username, options.password,
    options.remote_dir, options.local_dir, opti
    File "xx../shell/", line 17, in __init__
    File "/opt/freeware/lib/python2.6/", line 536, in cwd
    cmd = 'CWD ' + dirname
    TypeError: cannot concatenate 'str' and 'NoneType' objects

    Source :

    #!/usr/bin/env python

    import ftplib
    import os

    class FTPSync(object):
    def __init__(self, host, username, password, ftp_base_dir,
    local_base_dir, delete=False): = host
    self.username = username
    self.password = password
    self.ftp_base_dir = ftp_base_dir
    self.local_base_dir = local_base_dir
    self.delete = delete

    self.conn = ftplib.FTP(host, username, password)
    except OSError:
    def get_dirs_files(self):
    dir_res = []
    self.conn.dir('.', dir_res.append)
    files = [f.split(None, 8)[-1] for f in dir_res if
    dirs = [f.split(None, 8)[-1] for f in dir_res if
    return (files, dirs)
    def walk(self, next_dir):
    print "Walking to", next_dir
    except OSError:

    ftp_curr_dir = self.conn.pwd()
    local_curr_dir = os.getcwd()

    files, dirs = self.get_dirs_files()
    print "FILES:", files
    print "DIRS:", dirs
    for f in files:
    print next_dir, ':', f
    outf = open(f, 'wb')
    self.conn.retrbinary('RETR %s' % f, outf.write)
    if self.delete:
    print "Deleting", f
    for d in dirs:

    def run(self):

    if __name__ == '__main__':
    from optparse import OptionParser
    parser = OptionParser()
    parser.add_option("-o", "--host", dest="host",
    action='store', help="FTP host")
    parser.add_option("-u", "--username", dest="username",
    action='store', help="FTP username")
    parser.add_option("-p", "--password", dest="password",
    action='store', help="FTP password")
    parser.add_option("-r", "--remote_dir", dest="remote_dir",
    action='store', help="FTP remote starting directory")
    parser.add_option("-l", "--local_dir", dest="local_dir",
    action='store', help="Local starting directory")
    parser.add_option("-d", "--delete", dest="delete", default=False,
    action='store_true', help="use regex parser")

    (options, args) = parser.parse_args()
    f = FTPSync(, options.username, options.password,
    options.remote_dir, options.local_dir, options.delete)
    moonhkt, Sep 16, 2012
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  2. comment the next line , then print the parameters and see what they
    are. That should get you started.
    f = print(, options.username, options.password,
    options.remote_dir, options.local_dir, options.delete)
    Joel Goldstick, Sep 16, 2012
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  3. Hi! Thanks for this, good information to open with.
    NoneType is the type of the singleton object None. Why are you getting
    None where you ought to be providing a directory name? Heavily trimmed
    code follows:
    If you don't pass -r/--remote_dir to your script, then (presumably - I
    haven't actually used optparse so this is glarked from context)
    options.remote_dir is being set to, or left at, None. A quick look at
    the docs suggests that one solution is to add a default value to the

    Alternatively, treat the options as mandatory, and provide them on the
    command line.

    Side point: When you go to the docs page there, you may notice that
    optparse is deprecated in favour of argparse. May as well continue the
    tutorial with what they recommend, but it's probably worth having a
    look at argparse eventually.

    Hope that helps!

    Chris Angelico
    Chris Angelico, Sep 16, 2012
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