Parsing Large Xml Using Iterparse() Consumes Too Much Memory. Any Alternative?

I am using python 2.7 with latest lxml library. I am parsing a large XML file with very homogenous structure and millions of elements. I thought lxml's iterparse would not build an

Solution 1:

Try using Liza Daly's fast_iter:

deffast_iter(context, func, args=[], kwargs={}):
    # http://www.ibm.com/developerworks/xml/library/x-hiperfparse/# Author: Liza Dalyfor event, elem in context:
        func(elem, *args, **kwargs)
        elem.clear()
        while elem.getprevious() isnotNone:
            del elem.getparent()[0]
    del context

fast_iter removes elements from the tree after they have been parsed, and also previous elements (maybe with other tags) that are no longer needed.

It could be used like this:

import lxml.etree as ET
defprocess_element(elem):
    ...
context=ET.iterparse(filename, events=('end',), tag=...)        
fast_iter(context, process_element)

Solution 2:

I had this problem and solved it with a hint from http://effbot.org/zone/element-iterparse.htm#incremental-parsing:

elems = ET.Element('MyElements')
forevent, elem in ET.iterparse(filename):
    ifis_needed(elem): # implement this condition however you like
        elems.append(elem)
    else:
        elem.clear()

This gives you a tree with only the elements you need, without requiring unnecessary memory during parsing.