% married by per capita, where per capita is defined as an individual > 18 years old.

census.py

import requests
import json


def test_api():
    state_list = list(range(1, 52))
    key = '76e9012372312829bbfd506cd2b9dcff63c58e75'
    params = 'NAME,P0180003,P0100001'
    url = 'http://api.census.gov/data/2010/sf1?key={0}&get={1}&for=state:{2}'
    state_data = []
    for state in state_list:
        r = requests.get(url.format(key, params, str(state).zfill(2)))
        if r.text:
            data = json.loads(r.text)[1]
            state, num_households, total_population_over_18 = (data[0], int(data[1]), int(data[2]))
            num_married = num_households * 2
            percentage_married = (num_married / total_population_over_18) * 100
            formed_data = {
                'state': state,
                'number_of_married': num_married,
                'total_population_over_18': total_population_over_18,
                'percentage_married': percentage_married
            }
            state_data.append(formed_data)

    if state_data:
        sorted_state_data = sorted(state_data, key=lambda k: k['percentage_married'], reverse=True)
        for index, state_data in enumerate(sorted_state_data):
            print(index + 1,
                  state_data['state'],
                  "{:.2f}%".format(state_data['percentage_married']))

test_api()

In order to run this script, you will need to install the requests module, via pip or by source. Then run python census.py and you'll see the full list of states, ranked by marriage percentage