Find the prime numbers in Python.

The program

Press Run to see what it prints. Change anything you like, then run it again.

for n in range(2, 51):
    is_prime = True
    for d in range(2, n):
        if n % d == 0:
            is_prime = False
            break
    if is_prime:
        print(n, end=" ")
print()

2 3 5 7 11 13 17 19 23 29 31 37 41 43 47 

How it works

1. A prime is a number bigger than 1 whose only factors are 1 and itself.
2. For each n, the inner loop tries every divisor d. As soon as one divides evenly, n is not prime and break leaves the inner loop.
3. end=" " keeps everything on one line, separated by spaces.

Try this

• Find primes up to 100.
• Count how many there are.
• Make the inner loop faster: only try divisors up to the square root of n.

Stuck on an error? Read how to debug Python.