Python program to print the first N prime numbers

In this tutorial, we will explore how to create a Python program to print the first N prime numbers. This program is essential if you encounter questions like, “How can you print 10 prime numbers in Python?” or “How do you print the first 7 prime numbers in Python?” Knowing how to write a Python program to print the first N prime numbers is crucial, as it provides a flexible solution for printing any desired number of prime numbers.

Example:
N = 5
Output should be:
2
3
5
7
11

According to the definition, a Prime number is a natural number greater than 1 (one), that has only two factors, 1 and itself. In other words, a positive integer, except for 1 (one), that is divisible only by 1 and itself is called a prime number. Two (2) is the only even prime number. Other even numbers are divisible by 2 or other even numbers, which is why they are not considered prime numbers.

Program 1: Python program to print the first N prime numbers using while and for loop

# Python program to print first N prime numbers
from math import isqrt

N = int(input("Please enter a positive number: "))

# count variable is used to count total printed prime number
count = 0
num = 2

# iterating while loop until count is less than N
while count < N:
    is_prime = True
    
    # iterating foor loop to check number is prime or not
    for i in range(2, isqrt(num) + 1):
        if num % i == 0:
            is_prime = False
            break
    
    # if is_prime True then number will be prime
    if is_prime:
        print(num)
        count += 1
    # increase num by 1 to check next number is prime or not
    num += 1
    

Output

Please enter a positive number: 10
2
3
5
7
11
13
17
19
23
29

Explanation:

Why do we utilize the square root of ‘num’ when iterating through the ‘for’ loop?
The main fact is that a composite number must have a factor less than or equal to the square root of that number. Otherwise, the number is not a prime number.

• The program begins by prompting the user to enter a positive number (N) using input(). The entered value is then converted to an integer using int().
• Two variables count and num are initialized. count is used to track the total number of printed prime numbers. num starts from 2, the first prime number.
• A while loop is used to iterate until the count of printed prime numbers (count) is less than the user-specified number (N).
• Inside the loop, a boolean variable is_prime is initialized as True for each iteration.
• A for loop is used to check whether the current number (num) is prime. It iterates from 2 to the square root of num (using isqrt for efficiency).
• If, is_prime is True, indicating that the current num is a prime number, it is printed. The count is then incremented.
• Regardless of whether the current number is prime or not, num is incremented by 1 to check the next number in the next iteration.
• The program continues iterating through the while loop until the specified number of prime numbers (N) is printed.

Program 2: Python program to print the first N prime numbers using the function

# Python program to print first N prime numbers using function
from math import isqrt

def is_prime_number(num):
    # check whether input number is less than 1 or not
    if num <= 1:
        return False
    
    # Check for factors from 2 to the square root of the number + 1
    for i in range(2, isqrt(num) + 1):
        # if number is divisble by any number from the range then it is not prime number
        if num % i == 0:
            return False
    return True

def print_n_prime_numbers(n):
    # count variable is used to count total printed prime number
    count = 0
    num = 2
    
    # iterating while loop until count is less than n
    while count < n:
        if is_prime_number(num):
            print(num)
            count += 1
        num += 1

# calling function to print prime number by taking input from the user for number of prime numbers.
N = int(input("Please enter a positive number: "))
print_n_prime_numbers(N)

Output

Please enter a positive number: 5
2
3
5
7
11

Explanation:

• The program starts by prompting the user to input a positive number (N) using the input() function. The user is expected to enter the desired count of prime numbers they want to be printed.
• The print_n_prime_numbers function is then called with the user-input value (N) as an argument. This function is responsible for printing the first N prime numbers.
• Inside the print_n_prime_numbers function, the provided value of N is used to determine how many prime numbers should be printed.
• The function initializes variables count and num to keep track of the total printed prime numbers and the current number being considered.
• It uses a while loop to continue the process until the count of printed prime numbers is less than N.
• Inside the loop, the is_prime_number function is called to check whether the current num is a prime number.
• If it is prime, the number is printed, and the count is incremented.
• The program prints the first N prime numbers based on the user’s input.
• The user gets a list of prime numbers according to their specified count (N).

You should also read:

• Python program to add two numbers
• Python program to add three numbers
• Find Prime Factors of an Integer Number in Python
• Python Program to Print All Prime Numbers in an Interval
• Python Program to Check Prime Number