check if number is prime in python code example
Example 1: determine if number is prime python
# Time Efficient Primality Check in Python
def primeCheck(n):
# 0, 1, even numbers greater than 2 are NOT PRIME
if n==1 or n==0 or (n % 2 == 0 and n > 2):
return "Not prime"
else:
# Not prime if divisable by another number less
# or equal to the square root of itself.
# n**(1/2) returns square root of n
for i in range(3, int(n**(1/2))+1, 2):
if n%i == 0:
return "Not prime"
return "Prime"
Example 2: python prime check
def isPrime(n):
if n<2: #1, 0 and all negative numbers are not prime
return False
elif n==2: #2 is prime but cannot be calculated with the formula below becuase of the range function
return True
else:
for i in range(2, n):
if (n % i) == 0: #if you can precisely divide a number by another number, it is not prime
return False
return True #if the progam dont return False and arrives here, it means it has checked all the numebrs smaller than n and nono of them divides n. So n is prime