Read XML file while it is being written (in Python)

Question

I have to monitor an XML file being written by a tool running all the day. But the XML file is properly completed and closed only at the end of the day.

Same constraint

Answer 1

Three hours after posting my question, no answer received. But I have finally implemented the simple example I was looking for.

My inspiration is from saaj's answer and is based on xml.sax and watchdog.

from __future__ import print_function, division
import time
import watchdog.events
import watchdog.observers
import xml.sax

class XmlStreamHandler(xml.sax.handler.ContentHandler):
  def startElement(self, tag, attributes):
    print(tag, 'attributes=', attributes.items())
    self.tag = tag
  def characters(self, content):
    print(self.tag, 'content=', content)

class XmlFileEventHandler(watchdog.events.PatternMatchingEventHandler):
  def __init__(self):
    watchdog.events.PatternMatchingEventHandler.__init__(self, patterns=['*.xml'])
    self.file = None
    self.parser = xml.sax.make_parser()
    self.parser.setContentHandler(XmlStreamHandler())
  def on_modified(self, event):
    if not self.file:
      self.file = open(event.src_path)
    self.parser.feed(self.file.read())

if __name__ == '__main__':
  observer = watchdog.observers.Observer()
  event_handler = XmlFileEventHandler()
  observer.schedule(event_handler, path='.')
  try:
    observer.start()
    while True:
      time.sleep(10)
  finally:
    observer.stop()
    observer.join()

While the script is running, do not forget to touch one XML file, or simulate the on-the-fly writing using the following command:

while read line; do echo $line; sleep 1; done out.xml &