Bear in mind that the LC will take all the memory needed at once, and that can bring some problems. You can also use a generator expresion (similar to a LC, but

Bear in mind that the LC will take all the memory needed at once, and that can bring some problems. You can also use a generator expresion (similar to a LC, but you use parenthesis instead of brackets) to avoid this problem, if you're expecting an iterable object and have no further need for the values after the computation is done: In [1]: (x*x for x in xrange(100)) Out[1]: <generator object <genexpr> at 0x0000000003558438> And the generator expression could be used inside a for loop in cases where de LC would be awkward or take more time (because you have to allocate memory for a billion numbers all at once, just to check those that are meet a certain requirement).