If it's something like the Mersenne Twister (in Python) then very very random. The period is something like 2^19937-1, and it passes a lot of tests to see wheth

If it's something like the Mersenne Twister (in Python) then very very random. The period is something like 2^19937-1, and it passes a lot of tests to see whether or not it looks random. Of course, in a big random system there are some states that simply won't be reached by any random number generator with a finite period. Once you start looking at combinations and permutations, you can a get staggeringly large number of states. But in practice, this shouldn't matter for any problem where Monte Carlo methods make sense - if your answer is very sensitive to whether or not you have sampled a state that only crops up one in a squillion times, you shouldn't use Monte Carlo.