python准备的请求-删除不需要的标头

Question

我在处理这个代码块时遇到了问题：

with requests.Session() as s:
    _hs = s.headers
    
    req = requests.Request('POST', url, data=json.dumps(data), headers=headers)
    prepared_req = req.prepare()
    if 'Content-Length' in prepared_req.headers:
        prepared_req.headers.pop('Content-Length')
    rsp = s.send(prepared_req, timeout=self._TIMEOUT)
    try:
        rsp.raise_for_status()
    except requests.HTTPError:
        self._logger.exception("error in retrieving response from %s -- response content: %s",
                                        url, rsp.content)
        raise
    return rsp.json()

Content-Length 已从 PreparedRequest 标头中正确删除，但在 send 期间出现问题：

Traceback (most recent call last):
  File "/opt/projects/MyProj/my-http-client/my_http_client/http_client.py", line 297, in _http_post
    rsp = s.send(prepared_req, timeout=self._TIMEOUT)
  File "/home/user/venvs/my-http-client-venv/lib/python3.8/site-packages/requests/sessions.py", line 655, in send
    r = adapter.send(request, **kwargs)
  File "/home/user/venvs/my-http-client-venv/lib/python3.8/site-packages/requests/adapters.py", line 472, in send
    low_conn.send(i)
  File "/usr/lib/python3.8/http/client.py", line 975, in send
    self.sock.sendall(d)
TypeError: a bytes-like object is required, not 'str'

如果我用del 删除标题，也会发生同样的事情：

del prepared_req.headers['Content-Length']

有人知道怎么回事吗？没有headers.pop，一切正常。

Answer 1

根据对相关question 的回答，在 python3 中，所有字符串默认为 Unicode，但通过网络发送时需要转换为字节。

我怀疑问题出在data=json.dumps 行上，因为转储数据会将其转换为字符串而不是字节：

In [1]: data=json.dumps(dict(a='somestring'))                                                                                                                                 

In [2]: data                                                                                                                                                                  
Out[3]: '{"a": "somestring"}'

In [4]: type(data)                                                                                                                                                            
Out[5]: str

解决方法是将字符串编码为字节：

In [6]: data=json.dumps(dict(a='somestring')).encode('utf-8')                                                                                                                 

In [7]: data                                                                                                                                                                  
Out[8]: b'{"a": "somestring"}'

In [9]: type(data)                                                                                                                                                            
Out[10]: bytes

Answer 2

试过了，现在我有了这个：

Traceback (most recent call last):
  File "/home/user/venvs/my-app-venv/lib/python3.8/site-packages/requests/adapters.py", line 470, in send
    low_conn.send(hex(len(i))[2:].encode('utf-8'))
TypeError: object of type 'int' has no len()

奇怪，在官方请求文档中删除标头的方式似乎正是这样 https://docs.python-requests.org/en/master/user/advanced/#prepared-requests