Federal Electoral Districts in Waterloo Region

waterloo_districts.geojson

waterloo_districts.py

from functools import reduce
import json

import fiona
import pyproj

# https://open.canada.ca/data/en/dataset/737be5ea-27cf-48a3-91d6-e835f11834b0
shp = "zip://federal_electoral_districts_boundaries_2015_shp_en.zip"

# fio info zip://federal_electoral_districts_boundaries_2015_shp_en.zip reports "EPSG:3347"
# "EPSG:4269" for geojson?
transformer = pyproj.Transformer.from_crs(crs_from="EPSG:3347", crs_to="EPSG:4269")

# https://www.elections.ca/content.aspx?section=res&dir=cir/list&document=index338&lang=e#list
waterloo_district_ids = (35016, 35045, 35046, 35047, 35112)


def reducer(value, function):
    """Use with reduce() to apply a sequence of functions to a value"""
    return function(value)


def district_id(feature):
    """Get FEDNUM property for a district"""
    return feature.get("properties", {}).get("FEDNUM", 0)


def coordinates(feature):
    """Get (Polygon) coordinates for a district"""
    return feature.get("geometry", {}).get("coordinates", [[(0, 0)]])


def transform(feature, transformer=transformer):
    """Transform each point in a Polygon"""
    feature["geometry"]["coordinates"] = [
        [transformer.transform(x, y) for x, y in ring]
        for ring in coordinates(feature)
    ]
    return feature


def swap_xy(feature):
    """Swap x/y coordinates; use after transform()"""
    feature["geometry"]["coordinates"] = [
        [(y, x, *z) for x, y, *z in ring] for ring in coordinates(feature)
    ]
    return feature


def geojson(features):
    """Build a GeoJSON object"""
    return json.dumps(dict(type="FeatureCollection", features=features))


if __name__ == "__main__":
    waterloo_districts = []
    with fiona.Env():
        with fiona.open(shp) as features:
            for feature in features:
                # filter for local districts
                if district_id(feature) in waterloo_district_ids:
                    waterloo_feature = reduce(reducer, (transform, swap_xy), feature)
                    waterloo_districts.append(waterloo_feature)

    # create a local copy
    with open("waterloo_districts.geojson", "w") as f:
        f.write(geojson(waterloo_districts))