# Sieve of Eratosthenes in Python

Hello All, I working on a python project and I am confused sieve of eratosthenes coding problem. The problem statement is Given a number n, print all primes smaller than or equal to n. It is also given that n is a small number.

A prime number is a number that is divisible by only two numbers β themselves and 1

Example:
Input: n =10
Output: 2 3 5 7

I have taken this code reference from here. Can anyone explain me with the help of this code, how sieve of eratosthenes program works? or explain with another example?

``````def isPrime(n):

# Corner case
if n <= 1 :
return False

# check from 2 to n-1
for i in range(2, n):
if n % i == 0:
return False

return True

# Function to print primes
def printPrime(n):
for i in range(2, n + 1):
if isPrime(i):
print(i, end = " ")
``````

This is a Processing forum, so hereβs something that uses Processing.py / Python Mode, that rearranges the example in a way you may find easier to comprehend β

``````# set framerate to 1 frame every 2 seconds
def setup(): frameRate(0.5)

def draw():
# loop through all of the numbers between 2 and framecount
for i in range(2, frameCount):
# divide the framecount by every number from 2 up to framecount
if frameCount % i == 0:
# if the remainder of any division is zero,
# the framecount divides evenly by i,
# therefore it is not a prime number
print(
'{} is not prime because it divides evenly into {}'.format(frameCount, i)
)
# exit the loop immediately and start again on the next frame
return
# if the loop didn't exit, the framecount is a prime number
print('{} is prime'.format(frameCount))

``````
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You may find this discussion interesting, which is on Python Software Foundation Discourse:

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