Example: stream oriented parsing of XML (pretty hacky!)

example.py

# Remixed from: http://www.dabeaz.com/coroutines/cosax.py
# Don't shy away from reading http://www.dabeaz.com/coroutines/ if the stuff below
# seems super weird.

from xml.sax import ContentHandler, parse
from collections import namedtuple

ElementStart = namedtuple('ElementStart', 'name attrs')
ElementEnd = namedtuple('ElementEnd', 'name')

class EventHandler(ContentHandler):
    def __init__(self, target):
        self.target = target
    def startElement(self, name, attrs):
        self.target.send(ElementStart(name, attrs._attrs))
    def endElement(self, name):
        self.target.send(ElementEnd(name))

def pull_tuples(tuples):
    while True:
        event = yield
        if isinstance(event, ElementStart) and event.name == 'vehicle':
            vid = event.attrs['id']
            edges = None
            while True:
                event = yield
                if isinstance(event, ElementStart) and event.name == 'route':
                    edges = event.attrs['edges']
                elif isinstance(event, ElementEnd) and event.name == 'vehicle':
                    tuples.append((vid, edges))
                    break

if __name__ == '__main__':
    from StringIO import StringIO

    results = []

    puller = pull_tuples(results)
    puller.next()

    x = """\
<root><foo />
<bar>
<vehicle id="1292442" depart="26060.00">
      <route edges="24449167#2 27659684#1 24686876#1"/>
</vehicle>
</bar>
<vehicle id="1292443" depart="26060.00">
      <route edges="24449167#2 27659684#1 24686876#1"/>
</vehicle>
<vehicle id="1292444" depart="26060.00">
      <route edges="24449167#2 27659684#1 24686876#1"/>
</vehicle>
</root>
"""

    parse(StringIO(x), EventHandler(puller))
    print results