Mersh.txt requirements file for pip

mersh.txt

Fiona==0.8
Pyproj==1.9.0
Shapely==1.2.14

with-pyproj-shapely.py

# Example of using Fiona, pyproj, and Shapely together. Install all of them like this:
#
# $ pip install -r https://gist.github.com/raw/1689767/34dedfd28546d41f8dbd7a08ccf2c8abf9ebdf6a/mersh.txt

import logging
import sys

from fiona import collection
from pyproj import Proj, transform
from shapely.geometry import mapping, shape


logging.basicConfig(stream=sys.stderr, level=logging.INFO)

with collection("docs/data/test_uk.shp", "r") as input:
    
    schema = input.schema.copy()
    p_in = Proj(input.crs)

    with collection(
            "with-pyproj-shapely.shp", "w", "ESRI Shapefile",
            schema=schema,
            crs={'init': "epsg:27700", 'no_defs': True}
            ) as output:
        
        p_out = Proj(output.crs)
        for f in input:
            
            try:

                # Transform the feature geometries.
                assert f['geometry']['type'] == "Polygon"
                new_coords = []
                for ring in f['geometry']['coordinates']:
                    x2, y2 = transform(p_in, p_out, *zip(*ring))
                    new_coords.append(zip(x2, y2))
                f['geometry']['coordinates'] = new_coords

                # Ensure that they are valid and "clean".
                geom = shape(f['geometry'])
                if not geom.is_valid:
                    clean = geom.buffer(0.0)
                    assert clean.is_valid
                    assert clean.geom_type == 'Polygon'
                    geom = clean
                f['geometry'] = mapping(geom)

                output.write(f)
            
            except Exception, e:
                # Writing uncleanable features to a different shapefile
                # is another option.
                logging.exception(
                    "Error transforming or cleaning feature %s:", f['id'])