A prime number is a natural number greater than 1 that has no positive divisors other than 1 or itself. Prime numbers play a fundamental role in various areas of mathematics and computer science. In this post, we will create a Python program that gets the user’s input. If this number is a prime number, it will return true; otherwise, it will return false. Creating a Prime number program is good to start in Python.
What is a Prime Number?
A prime number is any natural number that is greater than 1 that has no positive divisors other than 1 and itself. In simpler terms, a prime number is a whole number greater than 1 that cannot be formed by multiplying two smaller whole numbers. For example, 2,3,5,7,11, and 13 are prime numbers. These numbers are not divided by any other number except 1 and themselves.
Prime Numbers:
2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97, 101, 103, 107, 109, 113, 127, 131, 137, 139, 149, 151, 157, 163, 167, 173, 179, 181, 191, 193, 197, 199, etc.
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Checking Prime Numbers in Python Program
In this Python program, we will check if the number is prime or not. The following program demonstrates the Python program.
Program
# Python Program
def is_prime(number):
if number <= 1:
return False
for i in range(2, int(number**0.5) + 1):
if number % i == 0:
return False
return True
userInput = input("Enter the number from user ")
num = int(userInput)
if is_prime(num):
print(f"{num} is a prime number.")
else:
print(f"{num} is not a prime number.")
Output
Enter the number from user 4
4 is not a prime number.
Also Read: Lambda Function in Python
Finding Prime Number in Python using Flag Variable
In this program, we will use the flag variable to determine whether a number is prime or not. We will then print all prime numbers within a given range. In this example, we will use a loop to print the prime number.
Program
def is_prime(number):
if number <= 1:
return False
for i in range(2, int(number**0.5) + 1):
if number % i == 0:
return False
return True
start = 29
end = 100
for num in range(start, end+1):
if is_prime(num):
print(num, end=" ")
Output
29 31 37 41 43 47 53 59 61 67 71 73 79 83 89 97
Also Read: A Deep Dive Into Fibonacci Series in Python
Check the Prime Number using the Recursion
We can also find the prime number using the recursion. Recursion is the technique where we call the function itself. The following program demonstrates the Prime Number using Recursion in Python.
Program
def is_prime(n, i=2):
if n <= 2:
return n == 2
if n % i == 0:
return False
if i * i > n:
return True
return is_prime(n, i + 1)
# Python Program
inputUser = input("Enter the number using the number = ")
num = int(inputUser)
if is_prime(num):
print(f"{num} is a prime number.")
else:
print(f"{num} is not a prime number.")
Output
Enter the number using the number = 10
10 is not a prime number.
Also Read: Types of Arrays in Python
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Check the Prime Number using the while loop
In this program, we will use the while loop to check if the number is prime or not. The following program demonstrates is this number is prime or not
Program
def is_prime_while_loop(number):
if number <= 1:
return False
if number <= 3:
return True
if number % 2 == 0 or number % 3 == 0:
return False
i = 5
while i * i <= number:
if number % i == 0 or number % (i + 2) == 0:
return False
i += 6
return True
# Python Program
inputUser = input("Enter the number = ")
num = int(inputUser)
if is_prime_while_loop(num):
print(f"{num} is a prime number.")
else:
print(f"{num} is not a prime number.")
Output
Enter the number = 2
2 is a prime number.
Check the Prime Number using the Math module
In this program, we will use the Math module to find the prime number. If the number is prime, it will return true; otherwise, it will return false.
Progame
import math
def is_prime_check_with_math(number):
if number <= 1:
return False
if number <= 3:
return True
if number % 2 == 0 or number % 3 == 0:
return False
for i in range(5, int(math.sqrt(number)) + 1, 6):
if number % i == 0 or number % (i + 2) == 0:
return False
return True
# Test the function
inputUser = input("Enter the Number from user = ")
num = int(inputUser)
if is_prime_check_with_math(num):
print(f"{num} is a prime number.")
else:
print(f"{num} is not a prime number.")
Output
Enter the Number from user = 20
20 is not a prime number.
Check the Prime Number using the sympy.isprime() Method
In this program, we will use the sympy module. We can test whether a given number is prime or not using the sympy.isprime() function. The following program demonstrates the sympy.isPrime() method.
Program
from sympy import *
geek1 = isprime(30)
geek2 = isprime(13)
geek3 = isprime(2)
print(geek1) # check for 30 is prime or not
print(geek2) # check for 13 is prime or not
print(geek3) # check for 2 is prime or not
Output
False
True
True
Check the Prime Number using a for…else statement
In this program, we will use the for…else statement for checking the Prime Number in Python. The following program demonstrates the for ..else loop program in Python.
Program
def is_prime(num):
if num <= 1:
return False # Not a prime number
for i in range(2, int(num**0.5) + 1):
if num % i == 0:
return False
else:
return True
number = int(input("Enter the number = "))
if is_prime(number):
print(f"{number} is a prime number")
else:
print(f"{number} is not a prime number")
Output
Enter the number = 23
23 is a prime number
Check the Prime Number using the Trial Division Method
In this method, we will check if a number is prime by dividing it by all numbers from 2 to the square root of the number. The following program demonstrates the trial division method in the Python program.
Program
def is_prime_trial_division(number):
if number <= 1:
return False
if number <= 3:
return True
if number % 2 == 0 or number % 3 == 0:
return False
i = 5
while i * i <= number:
if number % i == 0 or number % (i + 2) == 0:
return False
i += 6
return True
# Test the function
num = int(input("Enter the Number from the User = "))
if is_prime_trial_division(num):
print(f"{num} is a prime number.")
else:
print(f"{num} is not a prime number.")
Output
Enter the Number from the User = 2
2 is a prime number.
Check the Prime Number using a Generator Function
In this program, we will check the number using the generator function in Python language. The following program demonstrates the 10 prime numbers indefinitely.
Program
def prime_generator():
yield 2
primes = [2]
current_number = 3
while True:
is_prime = all(current_number % prime != 0 for prime in primes)
if is_prime:
primes.append(current_number)
yield current_number
current_number += 2
generator = prime_generator()
for _ in range(10):
print(next(generator))
Output
2
3
5
7
11
13
17
19
23
29
Prime Factorization
In this program, we will find the prime factorisation of a number taken from the user. The following program demonstrates the Prime factorisation.
Program
def prime_factors(n):
factors = []
divisor = 2
while n > 1:
while n % divisor == 0:
factors.append(divisor)
n //= divisor
divisor += 1
return factors
number = int(input("Enter the number from the user = "))
factors = prime_factors(number)
print(f"Prime factors of {number}: {factors}")
Output
Enter the number from the user = 15
Prime factors of 15: [3, 5]
Sieve of Eratosthenes
The sieve of Eratosthenes is an algorithm for finding a prime number at a given limit. It was developed by the Greek astronomer Eratosthenes and is a very simple algorithm for computing the prime number.
The following program demonstrates this algorithm example.
Program
def sieve_of_eratosthenes(limit):
sieve = [True] * (limit + 1)
sieve[0:2] = [False, False]
p = 2
while p * p <= limit:
if sieve[p]:
for i in range(p * p, limit + 1, p):
sieve[i] = False
p += 1
primes = [i for i, is_prime in enumerate(sieve) if is_prime]
return primes
# Find and print all prime numbers up to 50
limit = int(input("Enter the limit of the number = "))
primes = sieve_of_eratosthenes(limit)
print(f"Prime numbers up to {limit}: {primes}")
Output
Enter the limit of the number = 30
Prime numbers up to 30: [2, 3, 5, 7, 11, 13, 17, 19, 23, 29]
Conclusion
In this article, we learned various techniques to find prime numbers in the Python programming language, such as Using the Math module, the while loop, and the Sympy module. Each method has its own advantages and use cases. Prime numbers, the building blocks of number theory, hold a central position in mathematics and commute science. If you want to explore Python language, check out the Accelerator Program in Business Analytics and Data Science.
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Updated on July 19, 2024