Python ftplib problems

Question

When I run this code from iPython 0.13:

import ftplib
f=ftplib.FTP('ftp://ftp.ncbi.nih.gov/genomes/Bacteria/')

I get the following error: gaierror: [Errno 8] nodename nor servname provided, or not known

The full error is below. I'm running python 2.7.1 on Mac OS X v10.7.5 (Lion). I've done some searching and it appears that in other situations similar error was generated. The strange part is I can do

import urllib2
tt= urllib2.urlopen('ftp://ftp.ncbi.nih.gov/genomes/Bacteria/')

and it works but if I could used the FTP functions I could avoid the parsing of the urlopen since my final goal is select a subset of directories and download their content.

Any idea how this error can be solved or bypassed? Thanks in Advance

---------------------------------------------------------------------------
gaierror                                  Traceback (most recent call last)
<ipython-input-2-91f3bda2d528> in <module>()
----> 1 f=ftplib.FTP('ftp://ftp.ncbi.nih.gov/genomes/Bacteria/')

/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/ftplib.pyc in        __init__(self, host, user, passwd, acct, timeout)
115         self.timeout = timeout
116         if host:
--> 117             self.connect(host)
118             if user:
119                 self.login(user, passwd, acct)

/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/ftplib.pyc in connect(self, host, port, timeout)
130         if timeout != -999:
131             self.timeout = timeout
--> 132         self.sock = socket.create_connection((self.host, self.port), self.timeout)
133         self.af = self.sock.family
134         self.file = self.sock.makefile('rb')

/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/socket.pyc in create_connection(address, timeout, source_address)
551     host, port = address
552     err = None
--> 553     for res in getaddrinfo(host, port, 0, SOCK_STREAM):
554         af, socktype, proto, canonname, sa = res
555         sock = None

gaierror: [Errno 8] nodename nor servname provided, or not known

Answer 1

The first argument to the FTP() constructor must be a hostname, not a URL:

f=ftplib.FTP('ftp.ncbi.nih.gov')
f.cwd('/genomes/Bacteria/')

(You probably need to login or provide a username/password in the FTP() call before calling cwd)