Code to convert OSM XML files with waypoints defining polygons into a shapefile with those polygons in it

osm_to_shapefile.py

import xml.etree.cElementTree as ET
from shapely.geometry import mapping, Polygon
import fiona
import os

input_filename = "villages.osm"
output_filename = "villages.shp"

# Parse the XML from the OSM file
tree = ET.ElementTree(file=input_filename)

# Get the root of the XML (the <osm> node)
r = tree.getroot()


# Get all of the individual points from the file into a dictionary,
# with the keys being the ids of the nodes
nodes = {}

# Put all nodes in a dictionary
for n in r.findall('node'):
	nodes[n.attrib['id']] = (float(n.attrib['lon']), float(n.attrib['lat']))


# Create a dictionary to hold the polygons we create
polygons = {}

# For each 'way' in the file
for way in r.findall("way"):

	coords = []

	# Look at all of the children of the <way> node
	for c in way.getchildren():
	    if c.tag == "nd":
	    	# If it's a <nd> tag then it refers to a node, so get the lat-lon of that node
	    	# using the dictionary we created earlier and append it to the co-ordinate list
	    	ll =  nodes[c.attrib['ref']]
	    	coords.append(ll)
	    if c.tag == "tag":
	    	# If it's a <tag> tag (confusing, huh?) then it'll have some useful information in it for us
	    	# Get out the information we want as an attribute (in this case village name - which could be
	    	# in any of a number of fields, so we check)
	    	if c.attrib['v'] not in ("residential", 'village'):
	    		village_name = c.attrib['v']

	# Take the list of co-ordinates and convert to a Shapely polygon
	polygons[village_name] = Polygon(coords)


# Set up the schema for the shapefile
# In this case we have two columns: id and name
schema = {
    'geometry': 'Polygon',
    'properties': {'id': 'int', 'name': 'str'},
}

# Remove the shapefile if it exists already
try:
	os.remove(output_filename)
except:
	pass

i = 0


# Write the shapefile
with fiona.open(output_filename, 'w', 'ESRI Shapefile', schema) as c:
	# For every polygon we stored earlier
    for name, p in polygons.iteritems():
		i += 1
		print "Writing: %s" % name
		# Write it to the shapefile
		c.write({
		    'geometry': mapping(p),
		    'properties': {'id': i, 'name': name},
		})