python prime number checker code example
Example 1: how to check if a number is prime in python
def prime(num):
for x in range(2,num):
if num % x == 0:
return False
return True
Example 2: 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 3: prime checker in python
#make the function
#to do this all hte vairibles go in side the function
def CheckIfPrime ():
a1 = input("which number do you want to check")
a = int(a1)#you need the checking number as an int not an str
b = 2 #the number to check againts
c = ("yes")
while b < a:#run the loop
if a%b == 0:#check if the division has a remainder
c = ("no")#set the answer
b = b+1
print(c)#print the output
CheckIfPrime ()#call the function
Example 4: check if a number is prime python
n=input('Enter the number you want to check: ')
try:
n=int(n)
except:
print('Wrong input.')
quit()
if n==1 or n==0:
print('This is neither prime nor composite')
else:
c=0
for i in range(2,n):
if n%i==0:
c=c+1
if c==0:
print("This is a prime number")
else:
print('This is a composite number.')
Example 5: 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