Python 3.X Shapely Polygon loaded from GeoJSON

Question

I'd like to use Shapely package to define a Polygon with the point coming from OpenStreetMap. Let's see an example.

From OpenStreetMap I have downloaded the following export.geojson that contains the points of the boundaries of NYC Hell's kitchen neightbourhood.

{
  "type": "FeatureCollection",
  "generator": "overpass-ide",
  "copyright": "The data included in this document is from www.openstreetmap.org. The data is made available under ODbL.",
  "timestamp": "2018-12-05T21:48:03Z",
  "features": [
    {
      "type": "Feature",
      "properties": {
        "@id": "relation/8398096",
        "admin_level": "10",
        "alt_name": "Midtown West",
        "boundary": "administrative",
        "name": "Hell's Kitchen",
        "place": "neighbourhood",
        "type": "boundary",
        "wikidata": "Q840133"
      },
      "geometry": {
        "type": "Polygon",
        "coordinates": [
          [
            [
              -73.996317,
              40.7533999
            ],
            [
              -73.9926276,
              40.7584281
            ],
            [
              -73.9897925,
              40.7572376
            ],
            [
              -73.9865711,
              40.7616564
            ],
            [
              -73.9828759,
              40.7667118
            ],
            [
              -73.9857128,
              40.7679195
            ],
            [
              -73.9847606,
              40.7692277
            ],
            [
              -73.993569,
              40.7729369
            ],
            [
              -73.9939928,
              40.7733086
            ],
            [
              -73.9941524,
              40.7733787
            ],
            [
              -73.9960903,
              40.7742003
            ],
            [
              -73.9963692,
              40.7738002
            ],
            [
              -73.9940733,
              40.7727927
            ],
            [
              -73.9942235,
              40.7725956
            ],
            [
              -73.99616,
              40.7733838
            ],
            [
              -73.9964068,
              40.7730913
            ],
            [
              -73.9946607,
              40.7723438
            ],
            [
              -73.9948565,
              40.7720959
            ],
            [
              -73.9969674,
              40.7729836
            ],
            [
              -73.9973322,
              40.7725205
            ],
            [
              -73.9952078,
              40.7716166
            ],
            [
              -73.995409,
              40.7713606
            ],
            [
              -73.995975,
              40.7716003
            ],
            [
              -73.9961976,
              40.7712915
            ],
            [
              -73.9959508,
              40.771188
            ],
            [
              -73.9959937,
              40.771129
            ],
            [
              -73.9956531,
              40.7709889
            ],
            [
              -73.9958328,
              40.7707451
            ],
            [
              -73.9959213,
              40.7707878
            ],
            [
              -73.9962056,
              40.7704465
            ],
            [
              -73.996093,
              40.7703896
            ],
            [
              -73.9963827,
              40.7699692
            ],
            [
              -73.9987564,
              40.7709279
            ],
            [
              -73.9991614,
              40.7703917
            ],
            [
              -73.9968413,
              40.769376
            ],
            [
              -73.9971685,
              40.7689454
            ],
            [
              -73.9995879,
              40.7699773
            ],
            [
              -74.0000251,
              40.7694248
            ],
            [
              -73.9967179,
              40.7680576
            ],
            [
              -73.9972463,
              40.7673263
            ],
            [
              -74.0005133,
              40.7687077
            ],
            [
              -74.0009397,
              40.7681714
            ],
            [
              -73.9976245,
              40.7667697
            ],
            [
              -73.998,
              40.76627
            ],
            [
              -73.9982522,
              40.766268
            ],
            [
              -74.0013501,
              40.7675681
            ],
            [
              -74.0019402,
              40.7668043
            ],
            [
              -73.9987242,
              40.7654147
            ],
            [
              -73.9989388,
              40.7652502
            ],
            [
              -73.9988717,
              40.7649861
            ],
            [
              -73.9991775,
              40.7649556
            ],
            [
              -74.0021253,
              40.7661115
            ],
            [
              -74.0026027,
              40.765498
            ],
            [
              -74.0024284,
              40.7654066
            ],
            [
              -74.0025812,
              40.7650897
            ],
            [
              -73.9995718,
              40.7638444
            ],
            [
              -74.000001,
              40.7636087
            ],
            [
              -74.0031847,
              40.7649516
            ],
            [
              -74.0034664,
              40.764594
            ],
            [
              -74.003225,
              40.7644721
            ],
            [
              -74.0033671,
              40.764273
            ],
            [
              -74.0012401,
              40.7633487
            ],
            [
              -74.0014815,
              40.7630358
            ],
            [
              -74.0036756,
              40.7639541
            ],
            [
              -74.0040135,
              40.7635214
            ],
            [
              -74.0018356,
              40.7625787
            ],
            [
              -74.0023103,
              40.7619571
            ],
            [
              -74.0045071,
              40.7628672
            ],
            [
              -74.004837,
              40.7624447
            ],
            [
              -74.0025732,
              40.7614573
            ],
            [
              -74.0028682,
              40.761051
            ],
            [
              -73.9964148,
              40.7583347
            ],
            [
              -73.9979787,
              40.7561892
            ],
            [
              -73.9991507,
              40.754582
            ],
            [
              -73.996317,
              40.7533999
            ]
          ]
        ]
      },
      "id": "relation/8398096"
    },
    {
      "type": "Feature",
      "properties": {
        "@id": "node/158852213",
        "@relations": [
          {
            "role": "label",
            "rel": 8398096,
            "reltags": {
              "admin_level": "10",
              "alt_name": "Midtown West",
              "boundary": "administrative",
              "name": "Hell's Kitchen",
              "place": "neighbourhood",
              "type": "boundary",
              "wikidata": "Q840133"
            }
          }
        ]
      },
      "geometry": {
        "type": "Point",
        "coordinates": [
          -73.9923918,
          40.7644228
        ]
      },
      "id": "node/158852213"
    }
  ]
}

Based on the Integration section of the documentation and the page 89 of this book, I get the following Python snippet to define the Polygon with the shape of Hell's kitchen:

from shapely.geometry import mapping, shape
I=shape(json.loads(open('/Users/MyUsername/Downloads/export.geojson').read()))
I.is_valid

but I am getting the following error:

Traceback (most recent call last): File "", line 1, in I.is_valid() NameError: name 'I' is not defined

I.is_valid Traceback (most recent call last): File "", line 1, in I.is_valid NameError: name 'I' is not defined Does anybody have an idea on how to fix it?

I don't think this is a duplicate question because this quesion is not about an external file in GeoJSON format.

maybe this helps https://gis.stackexchange.com/questions/246655/how-to-create-line-polygon-shapefiles-from-geojson-using-gdal-in-python — Khalil Al Hooti, Dec 05 '18 at 22:51

score 3 · Answer 1 · answered Aug 17 '21 at 16:07

I'm sure there's a better way to do so but this works for me:

import json
from shapely.geometry import Polygon


your_json_file = json.loads(open('export.geojson').read())

p1 = Polygon(your_json_file['features'][0]['geometry']['coordinates'][0])
print(p1)

score 1 · Accepted Answer · answered Aug 18 '21 at 14:31

Before I share my answer, I need to point out that this GeoJSON has two geometries: a polygon and a point. So whatever solution you come up with, you're going to have to find a way to parse the GeoJSON and only pick out specifically that Hell's Kitchen polygon.

A very straightforward way to read the GeoJSON is to use the geopandas library. This reads the contents of the GeoJSON into a GeoDataFrame, which is similar to a Pandas DataFrame, but with a few extra bells and whistles for geographic operations. It uses the shapely library to draw the actual geometries, which is what you really want.

Here's what the code would look like:

import geopandas as gpd

# Reading in the whole GeoJSON into a GeoDataFrame
gdf = gpd.read_file('/Users/MyUsername/Downloads/export.geojson')

# Getting the row that contains the Hell's Kitchen polygon
hk = gdf.loc[gdf['name'] == "Hell's Kitchen"].iloc[0]

# Getting the actual shapely geometry
hk_poly = hk['geometry']

In the code above, the variable hk_poly at the bottom of the code contains JUST the shapely geometry of the Hell's Kitchen neighborhood, as requested.

Python 3.X Shapely Polygon loaded from GeoJSON

2 Answers2