geocoding.py

def intersect(cur, sn1, sn2, sdr, inter_table):

    sn1_field = STREETNAME_FIELD
    if isinstance(sn1, int):
        sn1_field = 'norte'
    sn2_field = STREETNAME_FIELD
    if isinstance(sn2, int):
        sn2_field = 'norte'

    q = """
        with p1 as (

            select st_collect(geom) as p1
            from {str_table} str, {inter_table} inter
            where {sn1_field} = %(sn1)s
            and str.gid = inter.gid
            and inter.sdridu = %(sdr)s

        ), p2 as (

            select st_collect(geom) as p2
            from {str_table} str, {inter_table} inter
            where {sn2_field} = %(sn2)s
            and str.gid = inter.gid
            and inter.sdridu = %(sdr)s

        ), inter as (

            select st_intersection(p1, p2) as inter
            from p1, p2

        ), bb as (

            select st_envelope(inter) as bb
            from inter

        ), centroid as (

           select st_centroid(bb) as centroid
           from bb

        ), bb_radius_in_meters as (

           select st_distance(
               centroid::geography,
               st_setsrid(
                   st_makepoint(
                       st_xmin(bb),
                       st_ymin(bb)
                   ),
                   {srid}
               )::geography
           ) as bb_radius_in_meters
           from centroid, bb

        )

        select st_astext(centroid) as centroid,
               bb_radius_in_meters
        from centroid, bb_radius_in_meters
        where centroid is not null
        and bb_radius_in_meters is not null
    """

    q = q.format(
        sn1_field=sn1_field,
        sn2_field=sn2_field,
        str_table=STR_TABLE,
        inter_table=inter_table,
        srid=SRID
    )

    values = {'sn1': sn1, 'sn2': sn2, 'sdr': sdr}
    # print cur.mogrify(q, values)
    cur.execute(q, values)
    row = cur.fetchone()
    return {'coords': row['centroid'],
            'bb_radius': row['bb_radius_in_meters']} if row else {}