#!/usr/bin/env python
# -*- coding: utf-8 -*-
import psycopg2
import json
from geojson import loads, Feature, FeatureCollection
# Database Connection Info
db_host = "localhost"
db_user = "pluto"
db_passwd = "stars"
db_database = "py_geoan_cb"
db_port = "5432"
# connect to DB
conn = psycopg2.connect(host=db_host, user=db_user,
port=db_port, password=db_passwd, database=db_database)
# create a cursor
cur = conn.cursor()
# the PostGIS buffer query
buffer_query = """SELECT ST_AsGeoJSON(ST_Transform(
ST_Buffer(wkb_geometry, 100,'quad_segs=8'),4326))
AS geom, name
FROM geodata.schools"""
# execute the query
cur.execute(buffer_query)
# return all the rows, we expect more than one
dbRows = cur.fetchall()
# an empty list to hold each feature of our feature collection
new_geom_collection = []
# loop through each row in result query set and add to my feature collection
# assign name field to the GeoJSON properties
for each_poly in dbRows:
geom = each_poly[0]
name = each_poly[1]
geoj_geom = loads(geom)
myfeat = Feature(geometry=geoj_geom, properties={'name': name})
new_geom_collection.append(myfeat)
# use the geojson module to create the final Feature Collection of features created from for loop above
my_geojson = FeatureCollection(new_geom_collection)
# define the output folder and GeoJSon file name
output_geojson_buf = "../geodata/out_buff_100m.geojson"
# save geojson to a file in our geodata folder
def write_geojson():
fo = open(output_geojson_buf, "w")
fo.write(json.dumps(my_geojson))
fo.close()
# run the write function to actually create the GeoJSON file
write_geojson()
# close cursor
cur.close()
# close connection
conn.close()
