Requests is a great library for networking in Python with its friendly APIs and rich features. But today when I try to send a POST request to a website, using multipart form encoding, but without files, I got stuck and did not find my luck in the documentation either.

So after googling around, turns out there was some discussion in requests issue tracker already and the maintainers did not want to add explicit support for multipart for API consistency. However, this could be done indeed via use of some not well documented feature (See example first):

In [1]: data_req = Request('POST', 'https://franklingu.github.io/', data={'name
    ...: ': 'normal'}).prepare()

In [2]: print(data_req.body)
name=normal

In [3]: normal_multipart_req = Request('POST', 'https://franklingu.github.io/',
    ...:  files={'name': open('test.txt', 'r'), 'name2': 'content'}).pre
    ...: pare()

In [4]: print(normal_multipart_req.body.decode('utf-8'))
--cdf39af4e1bf449384b62fef701eda7b
Content-Disposition: form-data; name="name"; filename="name"

test


--cdf39af4e1bf449384b62fef701eda7b
Content-Disposition: form-data; name="name2"; filename="name2"

content
--cdf39af4e1bf449384b62fef701eda7b--


In [5]: no_file_multipart_req = Request('POST', 'https://franklingu.github.io/'
    ...: , files={'name2': (None, 'content')}).prepare()

In [6]: print(no_file_multipart_req.body.decode('utf-8'))
--32a85608b80a48bb8687e55b9cb26395
Content-Disposition: form-data; name="name2"

content
--32a85608b80a48bb8687e55b9cb26395--

So data_req is a normal POST request with urlencoded form data as body and this is what we usually need. And files can be POSTed using multipart form encoding as shown in normal_multipart_req. However, sometime we need multipart form data, but we do not need filename attribute there and therefore we will use the hidden syntax: use tuple as value for files dictionary: files = {'name': (<filename>, <file object>, <content type>, <per-part headers>)} and by setting filename to be None, we can mute the filename attribute. So in the final no_file_multipart_req we do not have filename in the entry.