Python:文件下载成功后，使用 ftplib 下载文件永远挂起

You will probably not get 1MB at a time, but instead something under 8KB. Let's assume you're seeing 1448, then 2896, 4344, etc.

• 如果您从 REST 中获得异常，则服务器不会处理恢复 - 放弃，您将被淹没.
• 如果文件超出实际文件大小，请点击 ^C，然后在十六进制编辑器中检查.
  • 如果您一遍又一遍地看到相同的 1448 字节或其他任何内容(您看到它打印出来的数量)，那您就完蛋了.
  • 如果您有正确的数据，但在每个 1448 字节的块之间有额外的字节，那实际上是可以修复的.如果您遇到这个问题并且无法弄清楚如何使用 f.seek 来解决它，我可以解释——但您可能不会遇到它.
  • If you get an exception from the REST, the server does not handle resuming—give up, you're hosed.
  • If the file goes on past the actual file size, hit ^C, and check it in a hex editor.
    • If you see the same 1448 bytes or whatever (the amount you saw it printing out) over and over again, again, you're hosed.
    • If you have the right data, but with extra bytes between each chunk of 1448 bytes, that's actually fixable. If you run into this and can't figure out how to fix it by using f.seek, I can explain—but you probably won't run into it.

    我们可以做的一件事是尝试中止下载并且不重新连接.

    One thing we can do is try to abort the download and not reconnect.

    def downit():
        with open('5MB.zip', 'wb') as f:
            ftp = FTP(host='speedtest.tele2.net', user='anonymous', passwd='test@example.com')
            while True:
                pos = f.tell()
                print(pos)
                ftp.sendcmd('TYPE I')
                sock = ftp.transfercmd('RETR 5MB.zip', rest=pos)
                buf = sock.recv(1024 * 1024)
                if not buf:
                    return
                f.write(buf)
                sock.close()
                ftp.abort()
    

    您将要尝试多种变体:

    • 没有sock.close.
    • 没有ftp.abort.
    • 在 ftp.abort 之后使用 sock.close.
    • 在 sock.close 之后使用 ftp.abort.
    • 上述所有四个重复，TYPE I 移到循环之前而不是每次.
    • No sock.close.
    • No ftp.abort.
    • With sock.close after ftp.abort.
    • With ftp.abort after sock.close.
    • All four of the above repeated with TYPE I moved to before the loop instead of each time.

    有些会引发异常.其他人只会看起来永远挂起.如果这对所有 8 个都是真的，我们需要放弃中止.但如果其中任何一个有效，那就太好了！

    Some will raise exceptions. Others will just appear to hang forever. If that's true for all 8 of them, we need to give up on aborting. But if any of them works, great!

    另一种加快速度的方法是在中止或重新连接之前一次下载 1MB(或更多).只需替换此代码:

    The other way to speed things up is to download 1MB (or more) at a time before aborting or reconnecting. Just replace this code:

    buf = sock.recv(1024 * 1024)
    if buf:
        f.write(buf)
    

    用这个:

    chunklen = 1024 * 1024
    while chunklen:
        print('   ', f.tell())
        buf = sock.recv(chunklen)
        if not buf:
            break
        f.write(buf)
        chunklen -= len(buf)
    

    现在，您不再为每次传输读取 1442 或 8192 字节，而是每次传输最多读取 1MB.试着把它推得更远.

    Now, instead of reading 1442 or 8192 bytes for each transfer, you're reading up to 1MB for each transfer. Try pushing it farther.

    例如，如果您的下载在 10MB 时失败，而您问题中的 keepalive 代码将大小增加到 512MB，但对于 3GB 来说还是不够，您可以将两者结合起来.使用 keepalive 一次读取 512MB，然后中止或重新连接并读取下一个 512MB，直到完成.

    If, say, your downloads were failing at 10MB, and the keepalive code in your question got things up to 512MB, but it just wasn't enough for 3GB—you can combine the two. Use keepalives to read 512MB at a time, then abort or reconnect and read the next 512MB, until you're done.