当我从 iPython 0.13 运行这段代码时：
import ftplib
f=ftplib.FTP('ftp://ftp.ncbi.nih.gov/genomes/Bacteria/')
我收到以下错误：gaierror: [Errno 8] nodename nor servname provided, or not known
完整的错误如下。我在 Mac OS X v10.7.5 (Lion) 上运行 python 2.7.1。我做了一些搜索，似乎在其他情况下也产生了类似的错误。奇怪的是我能做到
import urllib2
tt= urllib2.urlopen('ftp://ftp.ncbi.nih.gov/genomes/Bacteria/')
它可以工作，但如果我可以使用 FTP 功能，我可以避免解析 urlopen，因为我的最终目标是选择一个目录子集并下载它们的内容。
知道如何解决或绕过此错误吗？提前致谢
---------------------------------------------------------------------------
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