A port of https://github.com/peterjc/backports.lzma to cffi, which adds seeking support. If you compress your xz files with the --block-size option, you can use lzmaffi to efficiently seek through them.

This project was forked by PyPy and bundled with PyPy3, please report issues with the PyPy version to their issue tracker.

Example

import lzmaffi
import io

f = lzmaffi.open('log.xz', mode='rb')

# f has all the usual file object methods, like if you had used io.open
# It also has a block_boundaries property

for offset in f.block_boundaries:
	f.seek(offset)
	snippet = f.read(80)
	print "{0}: {1}...".format(offset, snippet)

# You can also seek to arbitrary locations
f.seek(-80, io.SEEK_END)
offset = f.tell()
snippet = f.read(80)
print "{0}: {1}...".format(offset, snippet)

Example output:

Tomers-MacBook-Pro:~ tomer$ python ex.py 
0: Let us now consider repetition clauses (like, while B repeat A or repeat A until...
400: ning pattern known as "induction" makes us well equipped to retain our intellect...
800: nal number of the corresponding current repetition. As repetition clauses (just ...
1200: program or by the dynamic evolution of the process) whether he wishes or not. Th...
1600: he number, n say, of people in an initially empty room, we can achieve this by i...
2000: nce that it becomes terribly hard to find a meaningful set of coordinates in whi...
2400: niquely by a counter counting the number of actions performed since program star...
2800:  stands is just too primitive; it is too much an invitation to make a mess of on...
3200: dinate system can be maintained to describe the process in a helpful and managea...
3600: early 1959 in Copenhagen quite explicitly expressed his doubts whether the go to...
4000: e use of the go to statement to alarm exits, but I have not been able to trace i...
4400: troducing a large number of labels in the program."
...
4372: t eliminates the need for introducing a large number of labels in the program."
...