The answer by Oscar is a 1-liner and I'd like to take nothing from it but, comparing strings is not the cleanest way to do this.
I like to use the simplejson library.
Specifically loads parses the natural json form of JavaScript to native Python types. So this technique can be used for a wider set of cases.
This will give you uniform code techniques which are easier to read, understand & maintain.
From the docs:
Deserialize s (a str or unicode instance containing a JSON document) to a Python object.
import simplejson as sjson
valid_python_var = sjson.loads(json_str_to_parse)
Or in the likely scenario that you are receiving it via parameter passing:
var_to_parse = request.POST.get('name_of_url_variable') #get url param
if var_to_parse is not None: #check if param was passed, not required
parsed_var = sjson.loads(var_to_parse) # loads does the work
Note: Import libraries using common sense, if you are going to use them once there is no need for it.