Yes, use parse_qs():
Parse a query string given as a string argument (data of type
application/x-www-form-urlencoded). Data are returned as a dictionary.
The dictionary keys are the unique query variable names and the values
are lists of values for each name.
>>> from urlparse import parse_qs
>>> url = 'http://example.com/json?key=12345&lat=52.370216&lon=4.895168&status=upcoming&radius=20&offset=0'
>>> parse_qs(url)['radius'][0]
'20'
UPD: as @DanielRoseman noted (see comments), you should first pass url through urlparse:
>>> from urlparse import parse_qs, urlparse
>>> parse_qs(urlparse(url).query)['radius'][0]
'20'