How to make python urllib2 follow redirect and keep post method

Question

I am using urllib2 to post data to a form. The problem is that the form replies with a 302 redirect. According to Python HTTPRedirectHandler the redirect handler will take the request and convert it from POST to GET and follow the 301 or 302. I would like to preserve the POST method and the data passed to the opener. I made an unsuccessful attempt at a custom HTTPRedirectHandler by simply adding data=req.get_data() to the new Request.

I am sure this has been done before so I thought I would make a post.

Note: this is similar to this post and this one but I don't want to prevent the redirect I just want to keep the POST data.

Here is my HTTPRedirectHandler that does not work

class MyHTTPRedirectHandler(urllib2.HTTPRedirectHandler):
def redirect_request(self, req, fp, code, msg, headers, newurl):
    """Return a Request or None in response to a redirect.

    This is called by the http_error_30x methods when a
    redirection response is received.  If a redirection should
    take place, return a new Request to allow http_error_30x to
    perform the redirect.  Otherwise, raise HTTPError if no-one
    else should try to handle this url.  Return None if you can't
    but another Handler might.
    """
    m = req.get_method()
    if (code in (301, 302, 303, 307) and m in ("GET", "HEAD")
        or code in (301, 302, 303) and m == "POST"):
        # Strictly (according to RFC 2616), 301 or 302 in response
        # to a POST MUST NOT cause a redirection without confirmation
        # from the user (of urllib2, in this case).  In practice,
        # essentially all clients do redirect in this case, so we
        # do the same.
        # be conciliant with URIs containing a space
        newurl = newurl.replace(' ', '%20')
        return Request(newurl,
                       headers=req.headers,
                       data=req.get_data(),
                       origin_req_host=req.get_origin_req_host(),
                       unverifiable=True)
    else:
        raise HTTPError(req.get_full_url(), code, msg, headers, fp)

Answer 1

This is actually a really bad thing to do the more I thought about it. For instance, if I submit a form to http://example.com/add (with post data to add a item) and the response is a 302 redirect to http://example.com/add and I post the same data that I posted the first time I will end up in an infinite loop. Not sure why I didn't think of this before. I'll leave the question here just as a warning to anyone else thinking about doing this.