keytree 1.1.0

读取KML

KML Placemark元素可以适配Python地理接口，然后与Shapely等软件包一起使用。

>>> data = """<?xml version="1.0" encoding="UTF-8"?>
... <kml xmlns="http://www.opengis.net/kml/2.2">
...   <Document>
...     <Placemark id="pm_1">
...       <name>point</name>
...       <Snippet>Point test</Snippet>
...       <Point>
...         <coordinates>
...           -122.364383,37.824664,0
...         </coordinates>
...       </Point>
...     </Placemark>
...   </Document>
... </kml>
... """
>>> from xml.etree import ElementTree
>>> doc = ElementTree.fromstring(data)
>>> kmlns = doc.tag.split('}')[0][1:]
>>> placemarks = doc.findall('*/{%s}Placemark' % kmlns)
>>> p0 = placemarks[0]
>>> import keytree
>>> f = keytree.feature(p0)
>>> print f.id, f.properties.name, f.properties.snippet
pm_1, point, Point test
>>>
>>> from shapely.geometry import shape
>>> s = shape(f.geometry)
>>> print s.buffer(1.5).exterior.length
9.4209934708642571

写入KML

提供Python地理接口的对象也可以转换为ElementTree API元素

>>> f = {
...     'id': 'pm_2',
...     'geometry': {
...         'type': 'Point',
...         'coordinates': (-122.364383, 37.824663999999999) },
...     'properties': {
...         'title': 'Feature 2',
...         'description': 'The second feature', }

keytree.element函数的第一个参数是XML上下文，创建的元素将与该元素具有相同的命名空间

>>> data = """<?xml version="1.0" encoding="UTF-8"?>
... <kml xmlns="http://www.opengis.net/kml/2.2">
...   <Document>
...   </Document>
... </kml>
... """
>>> doc = ElementTree.fromstring(data)
>>> elem = element(doc, f)
>>> print elem
<Element {http://www.opengis.net/kml/2.2}Placemark at ...>
>>> pprint(list(elem))
[<Element {http://www.opengis.net/kml/2.2}name at ...>,
 <Element {http://www.opengis.net/kml/2.2}Snippet at ...>,
 <Element {http://www.opengis.net/kml/2.2}description at ...>,
 <Element {http://www.opengis.net/kml/2.2}Point at ...>]

创建的元素不会自动添加到KML上下文，必须将其附加到适当的文档或文件夹

>>> doc[0].append(elem)
>>> print etree.tostring(doc)
<ns0:kml xmlns:ns0="http://www.opengis.net/kml/2.2">
  <ns0:Document>
    <ns0:Placemark id="pm_2">
      <ns0:name>Number 2</ns0:name>
      <ns0:Snippet>Placemark number 2</ns0:Snippet>
      <ns0:description />
      <ns0:Point>
        <ns0:coordinates>0.000000,0.000000,0.0</ns0:coordinates>
      </ns0:Point>
    </ns0:Placemark>
  </ns0:Document>
</ns0:kml>

KML助手

keytree.kml模块包含一些有用的实用函数

>>> from keytree.kml import kml_ns, findall_placemarks
>>> print kml_ns(doc)
{http://www.opengis.net/kml/2.2}
>>> findall_placemarks(doc)
[<Element {http://www.opengis.net/kml/2.2}Placemark at ...>]