Using MultipartPostHandler to POST form-data with Python

file, multipartform-data, python, upload, urllib2

Solution

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

Problem

Problem: When POSTing data with Python's urllib2, all data is URL encoded and sent as Content-Type: application/x-www-form-urlencoded. When uploading files, the Content-Type should instead be set to multipart/form-data and the contents be MIME-encoded. To get around this limitation some sharp coders created a library called MultipartPostHandler which creates an OpenerDirector you can use with urllib2 to mostly automatically POST with multipart/form-data. A copy of this library is here: MultipartPostHandler doesn't work for Unicode files I am new to Python and am unable to get this library to work. I wrote out essentially the following code. When I capture it in a local HTTP proxy, I can see that the data is still URL encoded and not multi-part MIME-encoded. Please help me figure out what I am doing wrong or a better way to get this done. Thanks :-) ``` FROM_ADDR = 'my@email.com' try: data = open(file, 'rb').read() except: print "Error: could not open file %s for reading" % file print "Check permissions on the file or folder it resides in" sys.exit(1) # Build the POST request url = "http://somedomain.com/?action=analyze" post_data = {} post_data['analysisType'] = 'file' post_data['executable'] = data post_data['notification'] = 'email' post_data['email'] = FROM_ADDR # MIME encode the POST payload opener = urllib2.build_opener(MultipartPostHandler.MultipartPostHandler) urllib2.install_opener(opener) request = urllib2.Request(url, post_data) request.set_proxy('127.0.0.1:8080', 'http') # For testing with Burp Proxy # Make the request and capture the response try: response = urllib2.urlopen(request) print response.geturl() except urllib2.URLError, e: print "File upload failed..." ``` EDIT1: Thanks for your response. I'm aware of the ActiveState httplib solution to this (I linked to it above). I'd rather abstract away the problem and use a minimal amount of code to continue using urllib2 how I have been. Any idea why the opener isn't being installed and used?

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