python从ftp上下载文件的方法：

首先导入ftp模块；

然后使用【chdir】命令切换工作路径；

再使用“self.ftp.nlst()”命令获取目录下的文件；

最后使用“self.ftp.retrbinary()”命令下载ftp文件即可。

#!/usr/bin/python
# coding=utf-8
import os
from ftplib import FTP # 引入ftp模块
class MyFtp:
  ftp = FTP()  
  def __init__(self,host,port=21):
    self.ftp.connect(host,port)  
  def login(self,username,pwd):
    self.ftp.set_debuglevel(2) # 打开调试级别2，显示详细信息    
    self.ftp.login(username,pwd)    
    p
rint(self.ftp.welcome)  
  def downloadFile(self,localpath,remotepath,filename):
    os.chdir(localpath)  # 切换工作路径到下载目录
    self.ftp.cwd( remotepath)  # 要登录的ftp目录
    self.ftp.nlst() # 获取目录下的文件
    file_handle = open(filename,"wb").write  # 以写模式在本地打开文件
    self.ftp.retrbinary('RETR %s' % os.path.basename(filename),file_handle,blocksize=1024) # 下载ftp文件
    # ftp.delete（filename） # 删除ftp服务器上的文件
  def close(self):
    self.ftp.set_debuglevel(0) # 关闭调试    
    self.ftp.quit()if __name__ == '__main__':
  ftp = MyFtp('host')
  ftp.login('username','pwd')
  ftp.downloadFile('E:\\RED\\workspace\\appAuto\\apk\\Android10','/mobile/Android/release10/','xxx.apk')
  ftp.close()

实例扩展：

#coding=utf-8
'''
 ftp自动下载、自动上传脚本，可以递归目录操作
'''

from ftplib import FTP
import os,sys,string,datetime,time
import socket

class MYFTP:
 def __init__(self, hostaddr, username, password, remotedir, port=21):
 self.hostaddr = hostaddr
 self.username = username
 self.password = password
 self.remotedir = remotedir
 self.port = port
 self.ftp = FTP()
 self.file_list = []
 # self.ftp.set_debuglevel(2)
 def __del__(self):
 self.ftp.close()
 # self.ftp.set_debuglevel(0)
 def login(self):
 ftp = self.ftp
 try: 
 timeout = 300
 socket.setdefaulttimeout(timeout)
 ftp.set_pasv(True)
 print u'开始连接到 %s' %(self.hostaddr)
 ftp.connect(self.hostaddr, self.port)
 print u'成功连接到 %s' %(self.hostaddr)
 print u'开始登录到 %s' %(self.hostaddr)
 ftp.login(self.username, self.password)
 print u'成功登录到 %s' %(self.hostaddr)
 debug_print(ftp.getwelcome())
 except Exception:
 print u'连接或登录失败'
 try:
 ftp.cwd(self.remotedir)
 except(Exception):
 print u'切换目录失败'

 def is_same_size(self, localfile, remotefile):
 try:
 remotefile_size = self.ftp.size(remotefile)
 except:
 remotefile_size = -1
 try:
 localfile_size = os.path.getsize(localfile)
 except:
 localfile_size = -1
 debug_print('localfile_size:%d remotefile_size:%d' %(localfile_size, remotefile_size),)
 if remotefile_size == localfile_size:
 return 1
 else:
 return 0
 def download_file(self, localfile, remotefile):
 if self.is_same_size(localfile, remotefile):
 debug_print(u'%s 文件大小相同，无需下载' %localfile)
 return
 else:
 debug_print(u'>>>>>>>>>>>>下载文件 %s ... ...' %localfile)
 #return
 file_handler = open(localfile, 'wb')
 self.ftp.retrbinary(u'RETR %s'%(remotefile), file_handler.write)
 file_handler.close()

 def download_files(self, localdir='./', remotedir='./'):
 try:
 self.ftp.cwd(remotedir)
 except:
 debug_print(u'目录%s不存在，继续...' %remotedir)
 return
 if not os.path.isdir(localdir):
 os.makedirs(localdir)
 debug_print(u'切换至目录 %s' %self.ftp.pwd())
 self.file_list = []
 self.ftp.dir(self.get_file_list)
 remotenames = self.file_list
 #print(remotenames)
 #return
 for item in remotenames:
 filetype = item[0]
 filename = item[1]
 local = os.path.join(localdir, filename)
 if filetype == 'd':
 self.download_files(local, filename)
 elif filetype == '-':
 self.download_file(local, filename)
 self.ftp.cwd('..')
 debug_print(u'返回上层目录 %s' %self.ftp.pwd())
 def upload_file(self, localfile, remotefile):
 if not os.path.isfile(localfile):
 return
 if self.is_same_size(localfile, remotefile):
 debug_print(u'跳过[相等]: %s' %localfile)
 return
 file_handler = open(localfile, 'rb')
 self.ftp.storbinary('STOR %s' %remotefile, file_handler)
 file_handler.close()
 debug_print(u'已传送: %s' %localfile)
 def upload_files(self, localdir='./', remotedir = './'):
 if not os.path.isdir(localdir):
 return
 localnames = os.listdir(localdir)
 self.ftp.cwd(remotedir)
 for item in localnames:
 src = os.path.join(localdir, item)
 if os.path.isdir(src):
 try:
 self.ftp.mkd(item)
 except:
 debug_print(u'目录已存在 %s' %item)
 self.upload_files(src, item)
 else:
 self.upload_file(src, item)
 self.ftp.cwd('..')

 def get_file_list(self, line):
 ret_arr = []
 file_arr = self.get_filename(line)
 if file_arr[1] not in ['.', '..']:
 self.file_list.append(file_arr)

 def get_filename(self, line):
 pos = line.rfind(':')
 while(line[pos] != ' '):
 pos += 1
 while(line[pos] == ' '):
 pos += 1
 file_arr = [line[0], line[pos:]]
 return file_arr
def debug_print(s):
 print s

if __name__ == '__main__':
 timenow = time.localtime()
 datenow = time.strftime('%Y-%m-%d', timenow)
 # 配置如下变量
 hostaddr = '211.15.113.45' # ftp地址
 username = 'UserName' # 用户名
 password = '123456' # 密码
 port = 21 # 端口号 
 rootdir_local = 'E:/mypiv' # 本地目录
 rootdir_remote = '/PIV'  # 远程目录

 f = MYFTP(hostaddr, username, password, rootdir_remote, port)
 f.login()
 f.download_files(rootdir_local, rootdir_remote)

 timenow = time.localtime()
 datenow = time.strftime('%Y-%m-%d', timenow)
 logstr = u"%s 成功执行了备份n" %datenow
 debug_print(logstr)

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