to print out prime numbers below certain integer.

1st_approach.py

number = int(input('input a number: '))

for candidate in range(2, number + 1):
    is_candidate_a_prime = True
    for i in range(2, candidate):
        if candidate % i == 0:
            is_candidate_a_prime = False
            break
    if is_candidate_a_prime:
        print(candidate)

2nd_approach.py

primes = [2, 3]

num = int(input('input a number: '))

for candidate in range(primes[-1] + 2, num + 1, 2):
    for prime in primes:
        if prime > candidate ** 0.5:
            primes.append(candidate)
            break
        if candidate % prime == 0:
            break

for prime in primes:
    if prime <= num:
        print(prime)
    else:
        break