Reading geoJSON newline-delimited file on Dynamo

Revit
,
1

Hi,

I have a geoJSON newline-delimited data file. It was created from QGIS, an OSM file with a height attribute in it. I want to parse that in Dynamo, create the polylines from the " geometry[coordinates] " column of the file to create buildings footprints, and extrude each building footprint by creating polycurve and extruding them according to the data in the “heights_max” column".

the file is like this: (data string):

{ “type”: “Feature”, “properties”: { “full_id”: “w1097381425”, “osm_id”: “1097381425”, “osm_uid”: “8150490”, “building”: null, “Heights_mean”: -3.8323120390415735, “Heights_min”: -6.0, “Heights_max”: 12 }, “geometry”: { “type”: “Polygon”, “coordinates”: [ [ [ 29.1476383, 40.8478408 ], [ 29.1476134, 40.8477578 ], [ 29.1476489, 40.8477517 ], [ 29.1476738, 40.8478347 ], [ 29.1476383, 40.8478408 ] ] ] } }

so I have searched how to parse geoJSON file and try to parse the file like this.

import json
data = json.loads(datastring)
data['geometry']["coordinates"]

so I tried writing this in Python script that works with a string input where I copied and pasted the contents of the geoJSON file

# Load the Python Standard and DesignScript Libraries
import sys
import clr
clr.AddReference('ProtoGeometry')
from Autodesk.DesignScript.Geometry import *

import json

# The inputs to this node will be stored as a list in the IN variables.
Text=IN[0]

# Place your code below this line
data = json.loads(Text)

# Assign your output to the OUT variable.
OUT =data["geometry"]["coordinates"]

but I couldn’t parse it. Could you help me to parse them?

ps: it is also said in the StackOverflow forum that using geopandas package may be better but I guess installing that package in Dynamo would be much harder way to parse it.

I tried using dataJSON package in dynamo.
I tried reading file like csv but get too many columns by that way.
Should I import the geoJSON file in Excel and convert it to CSV?

parsejson2.dyn (50.2 KB)

2

To help directly we would need the json file as well, otherwise we have to guess at what the data should be.

4

please_change_dyn_to_json.dyn (67.1 KB)

Hi,
I changed the extension to dyn from json to add here. Thank you.

1 Like
5

The json file is not correctly formatted, it is a series of json strings, one per line
You can iterate over the file like this

json_file = IN[0]

result = []
with open(json_file, "r") as jf:
    for line in jf:
        result.append(json.loads(line))

OUT = result
1 Like
6

thank you very much!

image
image1012×643 36.4 KB

2 Likes
7

There’s also this answer on Stack Overflow that is more fault tolerant, however requires a ‘readable’ object such as a file object

1 Like
8

Thank you again @Mike.Buttery @jacob.small

Today, when I tried to open the dyn file, Dynamo said there was an unknown error reading the file. Because the file contains "NodeLibraryDependencies": null after I worked. I changed it to this "NodeLibraryDependencies": [] then it is opened.

I am copying the script in case I need that again in the future.

# Load the Python Standard and DesignScript Libraries
import sys
import clr
clr.AddReference('ProtoGeometry')
from Autodesk.DesignScript.Geometry import *

import json

# The inputs to this node will be stored as a list in the IN variables.

json_file = IN[0]

# Place your code below this line

result = []
with open(json_file, "r") as jf:
    for line in jf:
        result.append(json.loads(line))

# Assign your output to the OUT variable.

OUT = result

I am also writing Mr Buttery’s other suggestion as a note, in case this one is needed in the future. But I couldn’t run this script, I need to work again for this one.

# Load the Python Standard and DesignScript Libraries
import sys
import clr
clr.AddReference('ProtoGeometry')
from Autodesk.DesignScript.Geometry import *

# The inputs to this node will be stored as a list in the IN variables.

fn = IN[0]

# Place your code below this line

def stream_read_json(fn):
    import json
    import re
    start_pos = 0
    with open(fn, 'r') as f:
        while True:
            try:
                obj = json.load(f)
                yield obj
                return
            except ValueError as e:
                f.seek(start_pos)
                end_pos = int(re.match('Extra data: line \d+ column \d+ .*\(char (\d+).*\)',
                                    e.args[0]).groups()[0])
                json_str = f.read(end_pos)
                obj = json.loads(json_str)
                start_pos += end_pos
                yield obj

# Assign your output to the OUT variable.

OUT =