二进制文件电子邮件附件问题

问题内容：

使用Python 3.1.2，我在发送二进制附件文件（jpeg，pdf等）时遇到问题-MIMEText附件可以正常工作。有问题的代码如下…

for file in self.attachments:
   part = MIMEBase('application', "octet-stream")
   part.set_payload(open(file,"rb").read())
   encoders.encode_base64(part)
   part.add_header('Content-Disposition', 'attachment; filename="%s"' % file)
   msg.attach(part)   # msg is an instance of MIMEMultipart()

server = smtplib.SMTP(host, port)
server.login(username, password)
server.sendmail(from_addr, all_recipients, msg.as_string())

但是，在调用堆栈的最下方（请参见下面的回溯），看起来msg.as_string（）已接收到一个附件，该附件创建了“字节”类型的有效负载而不是字符串。

有谁知道是什么原因引起的问题？任何帮助，将不胜感激。

艾伦

builtins.TypeError: string payload expected: <class 'bytes'>
File "c:\Dev\CommonPY\Scripts\email_send.py", line 147, in send
  server.sendmail(self.from_addr, all_recipients, msg.as_string())
File "c:\Program Files\Python31\Lib\email\message.py", line 136, in as_string
  g.flatten(self, unixfrom=unixfrom)
File "c:\Program Files\Python31\Lib\email\generator.py", line 76, in flatten
  self._write(msg)
File "c:\Program Files\Python31\Lib\email\generator.py", line 101, in _write
  self._dispatch(msg)
File "c:\Program Files\Python31\Lib\email\generator.py", line 127, in _dispatch
  meth(msg)
File "c:\Program Files\Python31\Lib\email\generator.py", line 181, in _handle_multipart
  g.flatten(part, unixfrom=False)
File "c:\Program Files\Python31\Lib\email\generator.py", line 76, in flatten
  self._write(msg)
File "c:\Program Files\Python31\Lib\email\generator.py", line 101, in _write
  self._dispatch(msg)
File "c:\Program Files\Python31\Lib\email\generator.py", line 127, in _dispatch
  meth(msg)
File "c:\Program Files\Python31\Lib\email\generator.py", line 155, in _handle_text
  raise TypeError('string payload expected: %s' % type(payload))

问题答案：

好的-经过无奈和网上搜索后，我发现问题是一个已知的错误，适用于Python
3.x，encoders.py，encode_base64函数，其内容应如下所示…

def encode_base64(msg):
    """Encode the message's payload in Base64.

    Also, add an appropriate Content-Transfer-Encoding header.
    """
    orig = msg.get_payload()
    encdata = _bencode(orig)

    # new line inserted to ensure all bytes characters are converted to ASCII
    encdata = str(encdata, "ASCII")

    msg.set_payload(encdata)
    msg['Content-Transfer-Encoding'] = 'base64'

该错误已作为问题＃4768提出，并于2010-05-10升级为严重状态。希望它将在下一版本（3.1.3？）中修复。

问候，艾伦

二进制文件电子邮件附件问题

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