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How can I directly retrieve only part of a JSON document, rather than extracting what I need from the whole thing?

I want to make a JSON request with the Python library requests where I only obtain certain JSON objects.
I know that it is really easy to process the JSON object obtained to only focus in the needed information, but that would throttle the request efficiency (in case it is done repeatedly).
As said, I know this is a possibility:
url = 'www.foo.com'
r = requests.get(url).json()
#Do something with r[3]['data4'], the only one who is going to be used.
But how could I directly only obtain r[3]['data4'] from the request?

Short Answer
To answer your question no, you can't but to understand why you need to know what is happening behind the scenes.
Behind the scenes
When you make a request such as r = requests.get('www.foo.bar') you are making a request to the server and you are viewing the result of that request when you do r.json(). This means that you cannot just get r[3]['data'] as you are parsing what the server sends to you unless the server only sends r[3]['data']. It may be possible to filter out everything else apart from that in the response processing but I am unaware of how to do it.

You can't, if the server does not allow it. If the target server allows you to specify fields you want then you can send that field list in your request and server will return you only those fields in JSON. Otherwise your will have to parse full JSON response and get your desired fields.

Request current route including query strings?

I've been looking in the Pyramid API and haven't been able to find a method that allows me to extract the url in the user's address bar, specifically including the query strings. Is there a method I keep skimming across?
http://docs.pylonsproject.org/projects/pyramid/dev/api/request.html

It sounds like you just want request.url which is whatever the user typed in the address bar.
request.GET is a dictionary of key/values in the query string.
request.POST is a dictionary of key/values in the request body.
request.params is a dictionary of the combination of both.
This might be better explained in the webob documentation, which is effectively what Pyramid is using for its request and response objects.
http://docs.webob.org/en/latest/index.html

Now one can use request.query_string if you only want the URL-encoded text after the ? (ie id=10&name=Bob)
http://docs.pylonsproject.org/projects/pyramid/en/latest/narr/webob.html

Best way to request-scope data in Django?

I'm wondering if there's a clever pattern for request-scoping arbitrary information without resorting to either TLS or putting the information in the session.
Really, this would be for contextual attributes that I'd like to not look up more than once in a request path, but which are tied to a request invocation and there's no good reason to let them thresh around in the session.
Something like a dict that's pinned to the request where I can shove things or lazy load them. I could write a wrapper for request and swap it out in a middleware, but I figured I'd check to see what best-practice might be here?

Just assign the dictionary directly to the request. You can do that in middleware or in your view, as you like.

Context processors. They are called once for every request and receive the actual request object - so you can add ANY data to the context, also based on the curent request!

using django-rest-interface with http put

I'm trying to figure out how to implement my first RESTful interface using Django and django-rest-interface. I'm having problems with the HTTP PUT requests.
How do I access the parameters of the PUT request?
I thought they would be in the request.POST array, as PUT is somewhat similar to POST in my understanding, but that array is always empty.
What am I doing wrong?
Thanks for the help

request.POST processes form-encoded data into a dictionary, which only makes sense for web browser form submissions. There is no equivalent for PUT, as web browsers don't PUT forms; the data submitted could have any content type. You'll need to get the raw data out of request.raw_post_data, possibly check the content type, and process it however makes sense for your application.
More information in this thread.

if you figure in the dispatch of ResourceBase there are a line like:
elif request_method == 'PUT':
load_put_and_files(request)
return target.update(request, *args, **kwargs)
load_put_and_files let prepare for you the request.PUT with the data y the request.method is PUT, so you dont have to worry about that...

What is the preferred way to redirect a request in Pylons without losing form data?

I'm trying to redirect/forward a Pylons request. The problem with using redirect_to is that form data gets dropped. I need to keep the POST form data intact as well as all request headers.
Is there a simple way to do this?

Receiving data from a POST depends on the web browser sending data along. When the web browser receives a redirect, it does not resend that data along. One solution would be to URL encode the data you want to keep and use that with a GET. In the worst case, you could always add the data you want to keep to the session and pass it that way.