Using MultipartPostHandler to POST form-data with Python

Solution 1:

It seems that the easiest and most compatible way to get around this problem is to use the 'poster' module.

# test_client.py
from poster.encode import multipart_encode
from poster.streaminghttp import register_openers
import urllib2

# Register the streaming http handlers with urllib2
register_openers()

# Start the multipart/form-data encoding of the file "DSC0001.jpg"
# "image1" is the name of the parameter, which is normally set
# via the "name" parameter of the HTML <input> tag.

# headers contains the necessary Content-Type and Content-Length
# datagen is a generator object that yields the encoded parameters
datagen, headers = multipart_encode({"image1": open("DSC0001.jpg")})

# Create the Request object
request = urllib2.Request("http://localhost:5000/upload_image", datagen, headers)
# Actually do the request, and get the response
print urllib2.urlopen(request).read()

This worked perfect and I didn't have to muck with httplib. The module is available here: http://atlee.ca/software/poster/index.html

Solution 2:

Found this recipe to post multipart using httplib directly (no external libraries involved)

import httplib
import mimetypes

def post_multipart(host, selector, fields, files):
    content_type, body = encode_multipart_formdata(fields, files)
    h = httplib.HTTP(host)
    h.putrequest('POST', selector)
    h.putheader('content-type', content_type)
    h.putheader('content-length', str(len(body)))
    h.endheaders()
    h.send(body)
    errcode, errmsg, headers = h.getreply()
    return h.file.read()

def encode_multipart_formdata(fields, files):
    LIMIT = '----------lImIt_of_THE_fIle_eW_$'
    CRLF = '\r\n'
    L = []
    for (key, value) in fields:
        L.append('--' + LIMIT)
        L.append('Content-Disposition: form-data; name="%s"' % key)
        L.append('')
        L.append(value)
    for (key, filename, value) in files:
        L.append('--' + LIMIT)
        L.append('Content-Disposition: form-data; name="%s"; filename="%s"' % (key, filename))
        L.append('Content-Type: %s' % get_content_type(filename))
        L.append('')
        L.append(value)
    L.append('--' + LIMIT + '--')
    L.append('')
    body = CRLF.join(L)
    content_type = 'multipart/form-data; boundary=%s' % LIMIT
    return content_type, body

def get_content_type(filename):
    return mimetypes.guess_type(filename)[0] or 'application/octet-stream'

Solution 3:

Just use python-requests, it will set proper headers and do upload for you:

import requests 
files = {"form_input_field_name": open("filename", "rb")}
requests.post("http://httpbin.org/post", files=files)

Solution 4:

I ran into the same problem and I needed to do a multipart form post without using external libraries. I wrote a whole blogpost about the issues I ran into.

I ended up using a modified version of http://code.activestate.com/recipes/146306/. The code in that url actually just appends the content of the file as a string, which can cause problems with binary files. Here's my working code.

import mimetools
import mimetypes
import io
import http
import json


form = MultiPartForm()
form.add_field("form_field", "my awesome data")

# Add a fake file     
form.add_file(key, os.path.basename(filepath),
    fileHandle=codecs.open("/path/to/my/file.zip", "rb"))

# Build the request
url = "http://www.example.com/endpoint"
schema, netloc, url, params, query, fragments = urlparse.urlparse(url)

try:
    form_buffer =  form.get_binary().getvalue()
    http = httplib.HTTPConnection(netloc)
    http.connect()
    http.putrequest("POST", url)
    http.putheader('Content-type',form.get_content_type())
    http.putheader('Content-length', str(len(form_buffer)))
    http.endheaders()
    http.send(form_buffer)
except socket.error, e:
    raise SystemExit(1)

r = http.getresponse()
if r.status == 200:
    return json.loads(r.read())
else:
    print('Upload failed (%s): %s' % (r.status, r.reason))

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 get_binary(self):
        """Return a binary buffer containing the form data, including attached files."""
        part_boundary = '--' + self.boundary

        binary = io.BytesIO()
        needsCLRF = False
        # Add the form fields
        for name, value in self.form_fields:
            if needsCLRF:
                binary.write('\r\n')
            needsCLRF = True

            block = [part_boundary,
              'Content-Disposition: form-data; name="%s"' % name,
              '',
              value
            ]
            binary.write('\r\n'.join(block))

        # Add the files to upload
        for field_name, filename, content_type, body in self.files:
            if needsCLRF:
                binary.write('\r\n')
            needsCLRF = True

            block = [part_boundary,
              str('Content-Disposition: file; name="%s"; filename="%s"' % \
              (field_name, filename)),
              'Content-Type: %s' % content_type,
              ''
              ]
            binary.write('\r\n'.join(block))
            binary.write('\r\n')
            binary.write(body)


        # add closing boundary marker,
        binary.write('\r\n--' + self.boundary + '--\r\n')
        return binary