编写Python脚本来实现最简单的FTP下载的教程

import os
from ftplib import FTP
 
class FTPSync():
 def __init__(self, host, usr, psw, log_file):
 self.host = host
 self.usr = usr
 self.psw = psw
 self.log_file = log_file
 
 def __ConnectServer(self):
 try:
 self.ftp = FTP(self.host)
 self.ftp.login(self.usr, self.psw)
 self.ftp.set_pasv(False)
 return True
 except Exception:
 return False
 
 def __CloseServer(self):
 try:
 self.ftp.quit()
 return True
 except Exception:
 return False
 
 def __CheckSizeEqual(self, remoteFile, localFile):
 try:
 remoteFileSize = self.ftp.size(remoteFile)
 localFileSize = os.path.getsize(localFile)
 if localFileSize == remoteFileSize:
 return True
 else:
 return False
 except Exception:
 return None
 
 def __DownloadFile(self, remoteFile, localFile):
 try:
 self.ftp.cwd(os.path.dirname(remoteFile))
 f = open(localFile, 'wb')
 remoteFileName = 'RETR ' + os.path.basename(remoteFile)
 self.ftp.retrbinary(remoteFileName, f.write)
 
 if self.__CheckSizeEqual(remoteFile, localFile):
 self.log_file.write('The File is downloaded successfully to %s' + '
' % localFile)
 return True
 else:
 self.log_file.write('The localFile %s size is not same with the remoteFile' + '
' % localFile)
 return False
 except Exception:
 return False
 
 def __DownloadFolder(self, remoteFolder, localFolder):
 try:
 fileList = []
 self.ftp.retrlines('NLST', fileList.append)
 for remoteFile in fileList:
 localFile = os.path.join(localFolder, remoteFile)
 return self.__DownloadFile(remoteFile, localFile)
 except Exception:
 return False
 
 def SyncFromFTP(self, remoteFolder, localFolder):
 self.__DownloadFolder(remoteFolder, localFolder)
 self.log_file.close()
 self.__CloseServer()