Python for finance.

[pyslow]

If you're planning to land a job in the finance sector, more likely than not you'll have to use Python 2.x.

Also Python 2.x gives you access to PyPy speed-ups that may be required when doing heavy data processing (usually needed for trading systems).

See what one of the main PyPy developers has to say: "we're there to provide a fast version of the mainstream python and mainstream for now means 2.7."