What it does

It reads the same way multpart/x contents. Lets say we have the following multipart/related content:

>>> import json

>>> from email.mime.multipart import MIMEMultipart
>>> from email.mime.base import MIMEBase

>>> multipart = MIMEMultipart('related')

>>> part = MIMEBase('application', 'json')
>>> part.set_payload(json.dumps({'foo': 'bar'}))
>>> multipart.attach(part)

>>> part = MIMEBase('application', 'octet-stream')
>>> part.set_payload(b"Python will save the world. I don't know how. But it will.")
>>> part.add_header('Content-Disposition', 'attachment', filename='python-save-the-world.txt')
>>> multipart.attach(part)

Here is how we can read it:

>>> import io

>>> from multipart_reader import MultipartReader

>>> content = multipart.as_string().split('\n\n', 1)[1]
>>> headers = dict(multipart.items())

>>> stream = io.BytesIO()
>>> stream.write(content)
>>> stream.seek(0)

>>> reader = MultipartReader(headers, stream)

>>> json_part = reader.next()
>>> json_part.json()
{'foo': 'bar'}

>>> file_part = reader.next()
>>> file_part.read()
"Python will save the world. I don't know how. But it will."

>>> file_part.filename
'python-save-the-world.txt'

That’s it …