64 lines
2.1 KiB
Python
64 lines
2.1 KiB
Python
'''
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geodata.osm.extract
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-------------------
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Extracts nodes/ways/relations, their metadata and dependencies
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from .osm XML files.
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'''
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from collections import OrderedDict
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from lxml import etree
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WAY_OFFSET = 10 ** 15
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RELATION_OFFSET = 2 * 10 ** 15
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ALL_OSM_TAGS = set(['node', 'way', 'relation'])
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WAYS_RELATIONS = set(['way', 'relation'])
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def parse_osm(filename, allowed_types=ALL_OSM_TAGS, dependencies=False):
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'''
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Parse a file in .osm format iteratively, generating tuples like:
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('node:1', OrderedDict([('lat', '12.34'), ('lon', '23.45')])),
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('node:2', OrderedDict([('lat', '12.34'), ('lon', '23.45')])),
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('node:3', OrderedDict([('lat', '12.34'), ('lon', '23.45')])),
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('node:4', OrderedDict([('lat', '12.34'), ('lon', '23.45')])),
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('way:4444', OrderedDict([('name', 'Main Street')]), [1,2,3,4])
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'''
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f = open(filename)
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parser = etree.iterparse(f)
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single_type = len(allowed_types) == 1
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for (_, elem) in parser:
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elem_id = long(elem.attrib.pop('id', 0))
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item_type = elem.tag
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if elem_id >= WAY_OFFSET and elem_id < RELATION_OFFSET:
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elem_id -= WAY_OFFSET
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item_type = 'way'
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elif elem_id >= RELATION_OFFSET:
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elem_id -= RELATION_OFFSET
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item_type = 'relation'
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if item_type in allowed_types:
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attrs = OrderedDict(elem.attrib)
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deps = [] if dependencies else None
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for e in elem.getchildren():
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if e.tag == 'tag':
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attrs[e.attrib['k']] = e.attrib['v']
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elif dependencies and item_type == 'way' and e.tag == 'nd':
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deps.append(long(e.attrib['ref']))
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elif dependencies and item_type == 'relation' and e.tag == 'member' and \
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e.attrib.get('type') in ('way', 'relation'):
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deps.append((long(e.attrib['ref']), e.attrib.get('role')))
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key = elem_id if single_type else '{}:{}'.format(item_type, elem_id)
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yield key, attrs, deps
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if elem.tag in ALL_OSM_TAGS:
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elem.clear()
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while elem.getprevious() is not None:
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del elem.getparent()[0]
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