Python 从公共 FTP 服务器下载 zip 文件

Question

我需要从Canada Government 的公共地理数据库在我的 PC（Windows 操作系统）上的文件夹“C:\DEMDownload”中下载几个（数字地球模型）zip 文件。

当我在ftp.retrbinary('RETR %s' %file, open(local_file, 'wb').write) 行运行我的代码时，我收到以下错误消息

Traceback (most recent call last):
  File "<input>", line 1, in <module>
  File "C:\Python27\lib\ftplib.py", line 414, in retrbinary
    conn = self.transfercmd(cmd, rest)
  File "C:\Python27\lib\ftplib.py", line 376, in transfercmd
    return self.ntransfercmd(cmd, rest)[0]
  File "C:\Python27\lib\ftplib.py", line 339, in ntransfercmd
    resp = self.sendcmd(cmd)
  File "C:\Python27\lib\ftplib.py", line 249, in sendcmd
    return self.getresp()
  File "C:\Python27\lib\ftplib.py", line 224, in getresp
    raise error_perm, resp
error_perm: 550 Failed to open file.

第二。是否可以避免编写 available_days 列表并创建所有要下载的 zip 文件的列表

import os, ftplib
destdir='C:\DEMDownload'
ftp = ftplib.FTP('ftp2.cits.rncan.gc.ca')
ftp.login('anonymous', '')
available_days= ['001k11.zip',
    '001k12.zip',
    '001k13.zip',
    '001k14.zip',
    '001k15.zip',
    '001l13.zip',
    '001l14.zip',
    '001l16.zip',
    '001m01.zip',
    '001m02.zip',
    '001m03.zip',
    '001m04.zip',
    '001m05.zip',
    '001m06.zip',
    '001m07.zip',
    '001m08.zip',
    '001m09.zip',
    '001m10.zip',
    '001m11.zip',
    '001m12.zip',
    '001m13.zip',
    '001m14.zip',
    '001m15.zip',
    '001m16.zip',
    '001n02.zip',
    '001n03.zip',
    '001n04.zip',
    '001n05.zip',
    '001n06.zip',
    '001n07.zip',
    '001n10.zip',
    '001n11.zip',
    '001n12.zip',
    '001n13.zip',
    '001n14.zip',
    '001n15.zip']

  hdfs = list()
  for day in available_days :
      file = available_days[available_days.index(day)]
      print 'file=', file
      local_file = os.path.join(destdir, file)
      ftp.retrbinary('RETR %s' %file, open(local_file, 'wb').write)
      hdfs.append(os.path.abspath(local_file))
      ftp.cwd('..')
  ftp.quit()

Answer 1

我能够使用您给定的网址成功下载 zip 文件：

# connect to ftp
url = urlparse.urlparse("http://ftp2.cits.rncan.gc.ca/pub/geobase/official/cded/50k_dem/")
ftp = ftplib.FTP(url.netloc)
ftp.login()
ftp.cwd(ftp_dirname)

with open(filename, 'w') as fobj:
    ftp.retrbinary('RETR %s' % basename, fobj.write)

您可以通过遍历 ftp 目录来避免硬编码的目录/文件名，类似于您可能通过一些创造性的使用 ftplib.FTP.dir() 遍历本地目录的方式

完整代码如下：

url = 'http://ftp2.cits.rncan.gc.ca/pub/geobase/official/cded/50k_dem/'
url = urlparse.urlparse(url)

local_root = os.path.expanduser("~/ftp_download") # change this to wherever you want to download to

def download(ftp, ftp_path, filename, check_cwd=True):
    """
    Using the given ftp connection, download from ftp_path to 
    filename. 

    If check_cwd is False, assume the ftp connection is already 
    in the correct current working directory (cwd)
    """
    basename = posixpath.basename(ftp_path)
    dirname = os.path.dirname(filename)
    if not os.path.exists(dirname):
        os.makedirs(dirname)
    if check_cwd:
        ftp_dirname = posixpath.dirname(ftp_path)
        if ftp_dirname != ftp.pwd():
            ftp.cwd(ftp_dirname)

    with open(filename, 'w') as fobj:
        ftp.retrbinary('RETR %s' % basename, fobj.write)

def ftp_dir(ftp):
    """
    Given a valid ftp connection, get a list of 2-tuples of the
    files in the ftp current working directory, where the first
    element is whether the file is a directory and the second 
    element is the filename.
    """
    # use a callback to grab the ftp.dir() output in a list
    dir_listing = []
    ftp.dir(lambda x: dir_listing.append(x))
    return [(line[0].upper() == 'D', line.rsplit()[-1]) for line in dir_listing]

# connect to ftp
ftp = ftplib.FTP(url.netloc)
ftp.login()

# recursively walk through the directory and download each file, depth first
stack = [url.path]
while stack:
    path = stack.pop()
    ftp.cwd(path)

    # add all directories to the queue
    children = ftp_dir(ftp)
    dirs = [posixpath.join(path, child[1]) for child in children if child[0]]
    files = [posixpath.join(path, child[1]) for child in children if not child[0]] 
    stack.extend(dirs[::-1]) # add dirs reversed so they are popped out in order

    # download all files in the directory
    for filepath in files:
        download(ftp, filepath, os.path.join(local_root, filepath.split(url.path,1)[-1]), 
                                             check_cwd=False)

# logout
ftp.quit()

您可以通过使用诸如ftptool 或ftputil 之类的python ftp 包装库之一来进一步压缩它