Converts a street address to a census tract number, based on current Census benchmark and vintage

census_getter.py

import requests
import urllib


def census_tract(street_address, city, state):
    """
    Accepts an address -- split into street number, city, and state -- and
    returns the census tract number as a string.

    Example:
         census_tract("2301 N Brazosport Blvd", "Freeport", "TX")
         >>> '664300'
    """
    base = "http://geocoding.geo.census.gov/geocoder/geographies/address"

    # The benchmark is the time period when Census created a snapshot of the
    # data (generally done twice a year). Public_AR_Current is the most recent
    # snapshot. The vintage of geography is the census or survey that the data
    # relates to. For example, Census2010_Census2010 are the address ranges
    # from the 2010 Census at the time of the 2010 Census.  We use the most
    # recent vintage.
    payload = dict(
        street=street_address,
        city=city,
        state=state,
        benchmark="Public_AR_Current",
        vintage="Current_Current",
        format="json"
    )

    r = requests.get(base + "?" + urllib.urlencode(payload))
    data = r.json()
    match = data['result']['addressMatches']

    if not match:
        return None
    else:
        # returns the result from the (zero-indexed) best match
        tracts = match[0]['geographies']['Census Tracts']
        return tracts[0]['TRACT']