def query_cell(self, event, context):
cities = []
resolution = h3.h3_get_resolution(event['h3_address'])
base_cell = str(h3.h3_get_base_cell(event['h3_address']))
if resolution < max_res:
max_query_res = resolution
else:
max_query_res = max_res
range_query = "#".join([
h3.h3_to_parent(event['h3_address'], x)
for x in range(min_res, max_query_res + 1)
])
key_condition_expression = "ParentCell = :parentcell AND begins_with(CellLocationIndex, :index)"
expression_values = {
":parentcell": {
"S": base_cell
},
":index": {
"S": range_query
}
}
resp = self.query_db_table(key_condition_expression, expression_values)
for item in resp['Items']:
city = item['CityName']['S']
if city not in cities:
cities.append(city)
return cities
def load_cities(self, event, context):
with open('usa_cities.geojson', 'r') as geoj:
cities = json.load(geoj)['features']
_db_table = dynamodb_resource.Table(db_table.name)
print("Loading database table")
with _db_table.batch_writer() as db_batch:
for idx, city in enumerate(cities):
city_id = str(idx)
if city['properties']['NAME']:
hexagons = h3.polyfill(city['geometry'],
max_res,
geo_json_conformant=True)
if len(hexagons) > 0:
for hex in hexagons:
parents = [
h3.h3_to_parent(hex, x)
for x in range(min_res, max_res + 1)
]
range_key = "#".join(parents) + "#{}".format(
city_id)
db_item = {
'ParentCell':
"{}".format(h3.h3_get_base_cell(hex)),
'CellLocationIndex':
range_key,
'CityName':
city['properties']['NAME'],
'CityID':
city_id
}
db_batch.put_item(Item=db_item)
if idx % 1000 == 0:
print("Processed {} cities".format(idx))
def test_h3_get_base_cell(self):
self.assertTrue(isinstance(h3.h3_get_base_cell('8928308280fffff'),
int))