How should I make my python PRNG work properly?

Everything I find says to use the Random module, but I want to do it from scratch. How would I do that?

I've done some work with messing with the Time module, and muddling the numbers to try to get a random(ish) result. (Returns a Boolean depending on if the rounded final result is divisible by two.)

My original function seems to fluctuate quite a bit. Yesterday it was around a 50/50 split, but now it's only about 10/90.

I'm trying to get it stable, but now it is always returning True 100% of the time...