Python 3 Sieve of Eratosthenes - https://upload.wikimedia.org/wikipedia/commons/b/b9/Sieve_of_Eratosthenes_animation.gif

sieve.py

def sieve(limit):
    candidates = set(range(2, limit + 1))

    for i in candidates:
        sieved = set(filter(lambda x: not x % i, candidates - {i}))
        candidates = candidates - sieved

    return sorted(candidates)
    
    
print(sieve(997))

It turns out you're looping over all the original candidate set.

Some different approaches to avoid this https://gist.github.com/tomviner/ddb9474f96f8d0366f5f39bf53208a16 plus an even more concise version.