Efficient reading of 800 GB XML file in Python 2.7

I am reading an 800 GB xml file in python 2.7 and parsing it with an etree iterative parser.

Currently, I am just using open('foo.txt') with no buffering argument. I am a little confused whether this is the approach I should take or I should use a buffering argument or use something from io like io.BufferedReader or io.open or io.TextIOBase.

A point in the right direction would be much appreciated.