利用python怎么将ftp文件下载到本地

#!/usr/bin/python
# -*- coding: utf-8 -*-
"""
FTP常用操作
"""
from ftplib import FTP
import os
class FTP_OP(object):
  def __init__(self, host, username, password, port):
    """
    初始化ftp
  :param host: ftp主机ip
  :param username: ftp用户名
  :param password: ftp密码
  :param port: ftp端口 （默认21）
  """
    self.host = host
    self.username = username
    self.password = password
    self.port = port
  def ftp_connect(self):
    """
    连接ftp
    :return:
    """
    ftp = FTP()
    ftp.set_debuglevel(1) # 不开启调试模式
    ftp.connect(host=self.host, port=self.port) # 连接ftp
    ftp.login(self.username, self.password) # 登录ftp
    ftp.set_pasv(False)##ftp有主动 被动模式 需要调整 
    return ftp
  def download_file(self, ftp_file_path, dst_file_path):
    """
    从ftp下载文件到本地
    :param ftp_file_path: ftp下载文件路径
    :param dst_file_path: 本地存放路径
    :return:
    """
    buffer_size = 102400 #默认是8192
    ftp = self.ftp_connect()
    print(ftp.getwelcome() ) #显示登录ftp信息
    file_list = ftp.nlst(ftp_file_path)
    for file_name in file_list:
      print("file_name"+file_name)
      ftp_file = os.path.join(ftp_file_path, file_name)
      print("ftp_file:"+ftp_file)
      #write_file = os.path.join(dst_file_path, file_name)
      write_file = dst_file_path+file_name ##在这里如果使用os.path.join 进行拼接的话 会丢失dst_file_path路径,与上面的拼接路径不一样
      print("write_file"+write_file)
      if file_name.find('.png')>-1 and not os.path.exists(write_file):
        print("file_name:"+file_name)
        #ftp_file = os.path.join(ftp_file_path, file_name)
        #write_file = os.path.join(dst_file_path, file_name)
        with open(write_file, "wb") as f:
          ftp.retrbinary('RETR %s' % ftp_file, f.write, buffer_size)
          #f.close()
    ftp.quit()

if __name__ == '__main__':
  host = "192.168.110.**"
  username = "****"
  password = "****"
  port = 21
  ftp_file_path = "/erp-mall/" #FTP目录
  dst_file_path = "/root/11" #本地目录
  ftp = FTP_OP(host=host, username=username, password=password, port=port)
  ftp.download_file(ftp_file_path=ftp_file_path, dst_file_path=dst_file_path)