I’ve found that lots of console.log calls on clojurescript objects will slow things down to a grind since stringifying them is nontrivial – be wary of this when doing debug logging and only output what you need to.

List comprehensions. They’re usually faster than equivalent for loops and don’t leave any state hanging around. And they have less LOC. Sometimes map can be faster, depending on what you’re doing (invoking functions is costly either way, so list comprehensions that allow you to remove lambdas are a win).

Further discussion here http://stackoverflow.com/questions/1247486/python-list-comprehension-vs-map

General loop optimisation, straight from Guido himself: http://www.python.org/doc/essays/list2str.html

And general tips: http://wiki.python.org/moin/PythonSpeed/PerformanceTips