Parsing blank XML tags with LXML and Python

Question

When parsing XML documents in the format of:

    Blue
    Chevy
    Camaro         


        

Answer 1

You're putting in a [text()] filter which explicitly asks only for elements which have text nodes them... and then you're unhappy when it doesn't give you elements without text nodes?

Leave that filter out, and you'll get your model element:

>>> s='''
... 
...   
...     Blue
...     Chevy
...     
...   
... '''
>>> e = lxml.etree.fromstring(s)
>>> carData = e.xpath('Car/node()')
>>> carData
[, , ]
>>> dict(((e.tag, e.text) for e in carData))
{'Color': 'Blue', 'Make': 'Chevy', 'Model': None}

That said -- if your immediate goal is to iterate over the nodes in the tree, you might consider using lxml.etree.iterparse() instead, which will avoid trying to build a full DOM tree in memory and otherwise be much more efficient than building a tree and then iterating over it with XPath. (Think SAX, but without the insane and painful API).

Implementing with iterparse could look like this:

def get_cars(infile):
    in_car = False
    current_car = {}
    for (event, element) in lxml.etree.iterparse(infile, events=('start', 'end')):
        if event == 'start':
            if element.tag == 'Car':
                in_car = True
                current_car = {}
            continue
        if not in_car: continue
        if element.tag == 'Car':
            yield current_car
            continue
        current_car[element.tag] = element.text

for car in get_cars(infile = cStringIO.StringIO('''BlueChevy''')):
  print car

...it's more code, but (if we weren't using StringIO for the example) it could process a file much larger than could fit in memory.