Refactoring the [neighborhood annotation script](https://github.com/codefornola/nola-neighborhood-annotation) to utilize [the nolabase](https://github.com/codefornola/nolabase/) instead of using all the data and doing the computation locally. This demonstrates using the nolabase as a dependency to a community run application or tool. Run it by p…

annotate.py

#!/usr/local/bin/python
# -*- coding: utf-8 -*-

# Refactoring the [neighborhood annotation script](https://github.com/codefornola/nola-neighborhood-annotation) to
# utilize [the nolabase](https://github.com/codefornola/nolabase/) instead of using all the data
# and doing the computation locally.
# This demonstrates using the nolabase as a dependency to a community run application or tool.
# Run it by passing a connection string and an input and output csv file:
# ```
# # get 2021 calls for service data as a test
# curl https://data.nola.gov/resource/3pha-hum9.csv > calls.csv
# python3 annotate.py postgresql://nolabaseuser:nolabasepassword@nolabase.codeforneworleans.org/nolabase calls.csv output.csv
# ```

import sys
import csv
import re
import psycopg2
from urllib.parse import urlparse

lat_lng_rg = re.compile('.*?([+-]?\\d*\\.\\d+)(?![-+0-9\\.]).*?([+-]?\\d*\\.\\d+)(?![-+0-9\\.])')

def parse_lat_lng(lat_lng_string):
    """
    Turns the Location column into (lat, lng) floats
    May look like this "(29.98645605, -90.06910049)"
    May have degree symbol "(29.98645605°,-90.06910049°)"
    """
    m = lat_lng_rg.search(lat_lng_string)

    if m:
        return (float(m.group(1)), float(m.group(2)))
    else:
        return (None, None)

# If I were to use this in production, I'd change this to be a batch
# call to the database instead of doing one row at a time
def find_neighborhood(conn, lat, lng):
    cur = conn.cursor()
    sql = """
            SELECT name FROM geometries.neighborhoods AS n WHERE
            st_within(ST_GeomFromText('POINT(%f %f)', 4326), n.geom) LIMIT 1
            """ % (lat, lng)
    cur.execute(sql)
    rows = cur.fetchone()
    if rows is None or len(rows) <= 0:
        return "N/A"
    return rows[0]

def annotate_csv(conn, in_file, out_file):
    """
    Goes row by row through the in_file and
    writes out the row to the out_file with
    the new Neighbhorhood column
    """

    reader = csv.reader(in_file)
    writer = csv.writer(out_file)

    # Write headers first, add new neighborhood column
    headers = next(reader)
    headers.append('Neighborhood')

    writer.writerow(headers)

    for row in reader:
        # WGS84 point, "Location" column, is last element
        lat, lng = parse_lat_lng(row[-1])

        if lat and lng:
            neighborhood = find_neighborhood(conn, lat, lng)
        else:
            neighborhood = 'N/A'

        row.append(neighborhood)
        writer.writerow(row)

        print("#%s lat: %s lng: %s -> %s" % (reader.line_num, lat, lng,
            neighborhood))


def print_help():
    help = """
    Usage:

    python annotate.py postgresql://username:password@nolabase.codefornola.org/nolabase input.csv output.csv
    """
    print(help)


if __name__ == '__main__':

    if len(sys.argv) < 3:
        print_help()
        sys.exit()
 
    parts = urlparse(sys.argv[1])

    conn = psycopg2.connect(
        user=parts.username,
        password=parts.password,
        dbname=parts.path[1:],
        host=parts.hostname,
        port=parts.port
    )

    in_file_path = sys.argv[2]
    out_file_path = sys.argv[3]

    with open(in_file_path, 'r') as in_file:
        with open(out_file_path, 'w') as out_file:
            annotate_csv(conn, in_file, out_file)