from ftplib import FTP
 
def download_file_from_ftp(ftp_server, username, password, remote_file, local_file):
    # 连接到FTP服务器
    with FTP(ftp_server) as ftp:
        ftp.login(user=username, passwd=password)
 
        # 切换到包含文件的目录（如果需要）
        # ftp.cwd('/path/to/directory')
 
        # 使用RETR命令下载文件
        with open(local_file, 'wb') as f:
            ftp.retrbinary('RETR ' + remote_file, f.write)
 
        print(f"File {remote_file} downloaded successfully.")
 
# 使用示例
ftp_server = 'ftp.example.com'
username = 'your_username'
password = 'your_password'
remote_file = '/path/to/remote/file.txt'
local_file = '/path/to/local/file.txt'
 
download_file_from_ftp(ftp_server, username, password, remote_file, local_file)