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Element

Several services, amongst them the OSMPythonTools.api and OSMPythonTools.overpass return OSM objects, which are represented by an instance of the class Element, which provides functions to access its properties.

Accessing general properties

Consider the following example of a query to the OSM Api:

from OSMPythonTools.api import Api
api = Api()
busStop = api.query('node/42467507')

The result, that is, busStop, is an element, whose properties can easily be access as follows:

busStop.id()
# 42467507
busStop.type()
# 'node'
busStop.lat()
# 40.701424
busStop.lon()
# -73.943064

Accessing tags

The tags can be accessed as a python dictionary:

busStop.tags()
# {'asset_ref': '2030', 'highway': 'bus_stop', 'location': 'Broadway / Thornton Street', 'name': 'Broadway / Thornton Street', 'route_ref': 'B46;B46-LTD'}

The value of a single tag can be accessed like follows:

busStop.tag('highway')
# 'bus_stop'

Accessing nodes and members

Ways incorporate nodes, and relations other elements, called members. Nodes of a way can easily be accessed:

way = api.query('way/108402486')
way.nodes()
# [<OSMPythonTools.api.ApiResult object at 0x104c06940>, <OSMPythonTools.api.ApiResult object at 0x104c2d8d0>, ...
way.nodes()[0].id()
# 1243967857

The members of a relation can also easily be accessed:

relation = api.query('relation/1539714')
relation.members()
# [<OSMPythonTools.api.ApiResult object at 0x104c20240>, <OSMPythonTools.api.ApiResult object at 0x104c2db38>, ...
relation.members()[0].id()
# 108402486

Accessing the geometry

In order to receive geometry information, the argument includeGeometry=True needs to be provided to the overpassQueryBuilder in order to let him generate a query that downloads the geometry data. As an example, one can query for all waterbodies in Vienna:

from OSMPythonTools.nominatim import Nominatim
from OSMPythonTools.overpass import overpassQueryBuilder, Overpass

vienna = Nominatim().query('Vienna, Austria')
query = overpassQueryBuilder(area=vienna.areaId(), elementType=['way', 'relation'], selector='"natural"="water"', includeGeometry=True)
result = Overpass().query(query)

The geometry of the downloaded elements can be obtained in the GeoJSON format:

result.elements()[0].geometry()
# {"coordinates": [[[16.498671, 48.27628], [16.4991, 48.276345], ... ]], "type": "Polygon"}

Some relations contain invalid geometries. If this is the case, an exception is returned.

Accessing the history and data about the creation

If explicitly queried, the resulting elements contain information about the history. As an example, one can query for the changes made by the user franz-benjamin in Heidelberg in March 2017:

from OSMPythonTools.nominatim import Nominatim
from OSMPythonTools.overpass import overpassQueryBuilder, Overpass

heidelberg = Nominatim().query('Heidelberg, Germany')
query = overpassQueryBuilder(area=heidelberg.areaId(), elementType='node', since='2017-01-01T00:00:00Z', to='2017-02-01T00:00:00Z', user='franz-benjamin', out='meta')
changedNodes = Overpass().query(query)

It is important to use out='meta' because this will fetch the meta data about the history and the creation of the corresponding elements:

changedNodes.elements()[0].version()
# 8
changedNodes.elements()[0].changeset()
# 44871772
changedNodes.elements()[0].user()
# 'franz-benjamin'
changedNodes.elements()[0].userid()
# 4913117
changedNodes.elements()[0].timestamp()
'2017-01-03T13:47:23Z'