Quickly determine if a number is prime in Python for numbers < 1 billion

Question

My current algorithm to check the primality of numbers in python is way to slow for numbers between 10 million and 1 billion. I want it to be improved knowing that I will never

Answer 1

You can first divide your n only by your primes_under_100.

Also, precompute more primes.

Also, you're actually store your range() result in memory - use irange() instead and use this memory for running Sieve of Eratosthenes algorithm.