Just a couple things:
sieve_list = list(range(end+1))
You don't actually need your list to be [0, 1, 2, ... ]
. You just need an indicator of whether or not it's true or false. So it's simpler just to start with:
sieve_list = [True] * (end + 1)
That'll likely perform better as well.
When you're iterating over multiples of primes, you're using:
range(each_number*2, end+1, each_number)
But we can do better than each_number*2
, we can start at each_number*each_number
. Every multiple of that prime between it and its square will already have been marked composite (because it will have a factor smaller than each_number
). That'll save a steadily larger increment of time each iteration.
As an optimization, we know up front that 2 and 3 are primes. So we can start our iteration at 5
and ensure that we only consider each_number
to not be multiples of 2 or 3. That is, alternate incrementing by 4 and 2. We can write this function:
def candidate_range(n):
cur = 5
incr = 2
while cur < n+1:
yield cur
cur += incr
incr ^= 6 # or incr = 6-incr, or however
Full solution:
def sieve(end):
prime_list = [2, 3]
sieve_list = [True] * (end+1)
for each_number in candidate_range(end):
if sieve_list[each_number]:
prime_list.append(each_number)
for multiple in range(each_number*each_number, end+1, each_number):
sieve_list[multiple] = False
return prime_list
Impact of various changes with end
at 1 million, run 10 times:
initial solution 6.34s
[True] * n 3.64s (!!)
Square over double 3.01s
candidate_range 2.46s
Also, I would consider every_multiple_of_the_prime
as an unnecessary long variable name, but YMMV.