In a discussion with Fredrik Lundh about his (c)ElementTree parser performance benchmarks on the lxml.etree implementation.

On my work linux/athlon box, with Python 2.3, I get the following figures:

library              time       space
-------------------------------------
ElementTree 1.2.4    1.3 s      14000k
cElementTree 0.8     0.12 s     5500k
etree (trunk)        0.12 s     11200k
readlines            0.08 s     4300k

The memory usage of cElementTree and ElementTree on my box are in the same range as Fredrik's benchmarks. lxml.etree obviously runs behind quite a bit, and little I can do about it as it's mostly libxml2 memory usage.

Note that these only measure parser performance, not anything else. One benefit that cElementTree gets here is that it constructs Python objects right away, while lxml.etree only does this later. This makes Fredrik's figures of course even more impressive. lxml.etree will have to compete in other areas than parser performance...