在python中使用lxml.objectify检查和修复附加到节点的值

Question

我正在尝试修改使用lxml.objectify的PyKML。通过附加跟踪节点，可以将其转换为具有默认str()行为的字符串。我想捕获列表或元组的附加内容，并将它们转换为适当的位置分隔行，而不是'(xx.xxxx，yy.yyyy)‘

from pykml.factory import GX_ElementMaker as GX

track = GX.Track(id='track_%d' % group_num )
for pt in group:
    when = datetime.datetime.utcfromtimestamp(pt['ts'])
    track.append( KML.when( when ) )  # WHEN?
for pt in group:
    track.append( GX.coord( (pt['x'],pt['y'])) )  # <-- trouble here

谢谢，-kurt

Answer 1

使用名称空间信息创建一个干净的ElementMaker类。然后，使用节点名称作为方法创建一个子类。在该方法中，处理所有奇怪的情况。然后手工将字符串放入节点名称所在的位置，并返回具有该节点名称的干净ElementMaker类的实例。

http://code.google.com/r/schwehr-pykml/source/browse/src/pykml/factory.py?spec=svn05a10cef3fd3c430389e8aca1313a20da932e565&r=05a10cef3fd3c430389e8aca1313a20da932e565

def indexable_levels(args):
    #print 'args:',args
    levels = 0
    while True:
        if isinstance(args,str): break
        try:
            args = args[0]
            levels += 1
        except:
            break
    #print '   levels ->',levels
    return levels

# Create a factory object for the KML Google Extension namespace
_GX_ElementMakerSimple = objectify.ElementMaker(
    annotate=False,
    namespace=nsmap['gx'],
    nsmap={'gx': nsmap['gx']},
)

class _GX_ElementMaker (objectify.ElementMaker):
    'KML ElementMaker with overloads for custom text payloads like coordinates'
    def coord(self, *args):
        #print 'start coord: "%s"' % (str(args)), type(args), len(args)
        levels = indexable_levels(args)
        if levels == 1 and len(args) == 1:
            # This case is really redundant with the next
            assert isinstance(args[0],str)
            return _GX_ElementMakerSimple.coord(args[0])
        if levels == 1:
            return _GX_ElementMakerSimple.coord(' '.join([str(item) for item in args]))
        if levels == 2:
            # ((-121.583851, 37.386052),)
            assert(len(args)==1)
            return _GX_ElementMakerSimple.coord(' '.join([str(item) for item in args[0] ]))
        assert(False)

# Create a factory object for the KML Google Extension namespace
GX_ElementMaker = _GX_ElementMaker(
    annotate=False,
    namespace=nsmap['gx'],
    nsmap={'gx': nsmap['gx']},
)