python urllib2 file upload

fileupload.py

import urllib2
import urllib

import itertools
import mimetools
import mimetypes
from cStringIO import StringIO

class MultiPartForm(object):
	"""Accumulate the data to be used when posting a form."""

	def __init__(self):
		self.form_fields = []
		self.files = []
		self.boundary = mimetools.choose_boundary()
		return
	
	def get_content_type(self):
		return 'multipart/form-data; boundary=%s' % self.boundary

	def add_field(self, name, value):
		"""Add a simple field to the form data."""
		self.form_fields.append((name, value))
		return

	def add_file(self, fieldname, filename, fileHandle, mimetype=None):
		"""Add a file to be uploaded."""
		body = fileHandle.read()
		if mimetype is None:
			mimetype = mimetypes.guess_type(filename)[0] or 'application/octet-stream'
		self.files.append((fieldname, filename, mimetype, body))
		return
	
	def __str__(self):
		"""Return a string representing the form data, including attached files."""
		# Build a list of lists, each containing "lines" of the
		# request.  Each part is separated by a boundary string.
		# Once the list is built, return a string where each
		# line is separated by '\r\n'.  
		parts = []
		part_boundary = '--' + self.boundary
		
		# Add the form fields
		parts.extend(
			[ part_boundary,
			  'Content-Disposition: form-data; name="%s"' % name,
			  '',
			  value,
			]
			for name, value in self.form_fields
			)
		
		# Add the files to upload
		parts.extend(
			[ part_boundary,
			  'Content-Disposition: file; name="%s"; filename="%s"' % \
				 (field_name, filename),
			  'Content-Type: %s' % content_type,
			  '',
			  body,
			]
			for field_name, filename, content_type, body in self.files
			)
		
		# Flatten the list and add closing boundary marker,
		# then return CR+LF separated data
		flattened = list(itertools.chain(*parts))
		flattened.append('--' + self.boundary + '--')
		flattened.append('')
		return '\r\n'.join(flattened)

url = "http://somewhere/upload.php"

headers = {
	'User-Agent'	: 'Mozilla/5.0',
	'Cookie'		: 'PHPSESSID=00000000000000000000000000'
}

def upload():
	form = MultiPartForm()
	form.add_field('subject', 'blahblahbalh')

	form.add_file('file', 'a.pdf',
		fileHandle=open('Dummy.pdf', 'rb'))		# from file
	#	fileHandle=StringIO('Dummy'))			# from string

	body = str(form)

	req = urllib2.Request(url, '', headers)
	
	req.add_header('Content-Type', form.get_content_type())
	req.add_header('Content-Length', len(body))
	req.add_data(body)

	return urllib2.urlopen(req).read()

upload()