About Python's built in sort() method

Sure! The code's here, starting with function islt and proceeding for QUITE a while;-). As Chris's comment suggests, it's C code. You'll also want to read this text file for a textual explanation, results, etc etc.

If you prefer reading Java code than C code, you could look at Joshua Bloch's implementation of timsort in and for Java (Joshua's also the guy who implemented, in 1997, the modified mergesort that's still used in Java, and one can hope that Java will eventually switch to his recent port of timsort).

Some explanation of the Java port of timsort is here, the diff is here (with pointers to all needed files), the key file is here -- FWIW, while I'm a better C programmer than Java programmer, in this case I find Joshua's Java code more readable overall than Tim's C code;-).

I just wanted to supply a very helpful link that I missed in Alex's otherwise comprehensive answer: A high-level explanation of Python's timsort (with graph visualizations!).

(Yes, the algorithm is basically known as Timsort now)

In early python-versions, the sort function implemented a modified version of quicksort. However, it was deemed unstable and as of 2.3 they switched to using an adaptive mergesort algorithm.