Find nth prime number in python

Hi, today we will learn about how to find an nth prime number in python. Finding a prime number is very easy in python. A prime number is a number which can only be divided by 1 and the number itself.

nth prime number in Python

prime number

Python program to find nth prime number

Code :

n = int(input('Enter : '))
prime_numbers = [2,3]
i=3

if(0<n<3):
    print(n,'th Prime Number is :',prime_numbers[n-1])
elif(n>2):
    while (True):
        i+=1
        status = True
        for j in range(2,int(i/2)+1):
            if(i%j==0):
                status = False
                break
        if(status==True):
            prime_numbers.append(i)
        if(len(prime_numbers)==n):
            break
    print(n,'th Prime Number is :', prime_numbers[n-1])
else:
    print('Please Enter A Valid Number')

 

Output :

Enter : 10
10 th Prime Number is : 29

Explanation :

  • At first, we take the input into the ‘n’ variable.
  • We create a python list variable ‘prime_numbers’.
  • Initially, we store 2,3 into the ‘prime_numbers’  variable.
  • We create an ‘i’ variable.  Initially, we store 3 into the ‘i’ variable.
  • We create an if condition. If the value of n is greater than 0 and less than 3, it means if the value of n in between 1 to 2 then the operation will be performed. If the condition satisfied then print the list prime_numbers’s n-1 th position value.
  • We create an elif condition. If the value is greater than 2 then the task is performed.
  • We create an infinite While Loop. For storing the prime number into the ‘prime_numbers’  variable.
  • increase the value of ‘i’ by one.
  • We create a boolean variable ‘status’. Initially, it is ‘True’.
  • We create a For Loop. The starting value of for loop variable ‘j’ is 2 and ending with (half+1) of the ‘i’ valueThis for loop is used for checking the ‘i’ number is prime or not prime.
  • If the remainder of  (‘i’ value / ‘j’ value) is Zero then it not be a prime number. And break the for loop and ‘status‘ will be ‘False’.
  • For all value of ‘j’, if the remainder not going to zero then the ‘status‘ will be ‘True’.
  • We check if the status True then it is a prime number.  And it stored into the ‘prime_numbers’.
  • We check if the length of the list is equal to the ‘n’ value then the while loop will break.
  • After breaking the while loop we print the nth prime number.
  • We create an else section if the user types any wrong or negative value then program will print ‘Please Enter A Valid Number’.

In this whole process, we can easily find the nth prime number.

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