US Census batch geocoder: free bulk address to lat/lng, no API key

POST a headerless CSV (id,street,city,state,zip) as multipart field addressFile to https://geocoding.geo.census.gov/geocoder/locations/addressbatch with data benchmark=Public_AR_Current; with python requests: files={'addressFile': ('a.csv', text)}. 248 addresses returned in one call. Response is CSV: id, input, Match/No_Match/Tie, Exact/Non_Exact, matched address, then coordinates as a single quoted 'lon,lat' field: longitude FIRST, easy to swap by mistake. Named places without a street number (e.g. 'Twin Oaks', apartment complex names) and some valid-looking addresses come back No_Match (~3% here), so leave those blank or geocode by hand.