twisted_upload_file.py

from collections import namedtuple
from urllib import urlencode
import os


FormFile = namedtuple('FormFile', 'filename, data')


def encode_form(fields, multipart=False, headers=None):
    headers = headers or {}

    if multipart:
        boundary = "%s" % os.urandom(20).encode('hex')
        start_boundary = '--' + boundary
        end_boundary = start_boundary + '--'

        headers = { 'Content-Type':'multipart/form-data; charset=utf-8; boundary=%s' % boundary }

        lines = []
        for name, value in fields.iteritems():
            lines.append(start_boundary)
            if isinstance(value, FormFile):
                lines.append('Content-Disposition: form-data; name="%s"; filename="%s"' % (name, value.filename))
                lines.append('Content-Type: application/octet-stream')
                value = value.data
            else:
                lines.append('Content-Disposition: form-data; name="%s"' % name)
                if not isinstance(value, basestring):
                    value = str(value)
            lines.append('')
            lines.append(value)
        lines.append(end_boundary)

        postdata = '\r\n'.join(lines)
    else:
        headers = { 'Content-Type':'application/x-www-form-urlencoded' }

        postdata = urlencode(fields)

    return headers, postdata

fields = OrderedDict([
    ('a', 'a'),
	('b', 'b'),
	('file', FormFile('filename', 'file content ... ...')),
])

header, postdata = encodeForm(fields)
url = 'http://...'
getPage(url, method='POST', headers=headers, postdata=postdata)