Prime numbers and python

6 Best Ways To Check If Number Is Prime In Python

This article will learn how to check if a number is prime or not in Python. Usually, we all know some common methods using library functions or without using library functions. But how many of us know that there are 6 ways to check a prime number. Maybe some of us will be familiar with some methods. But this article will teach you all the possible ways. Let us move on to check if a number is prime or not.

In the number system, we have two types of numbers. They are Prime and composite. Prime numbers are the numbers that are not the product of any other numbers. These numbers are always natural numbers. For example, 13 is a prime number. Because we cannot get this number as a product of any other two numbers except to the product of 1, on the other hand, if we take 4, it will show a result as a composite because it is a product of 2X2. I hope now all are clear about prime numbers.

The following methods are available:

6 Ways To Check If a Number Is Prime in Python

1: Using isprime()

Example:

def isprime(num): for n in range(2,int(num**0.5)+1): if num%n==0: return False return True print(isprime(7)) print(isprime(8))

This method is implemented using function. It will return True if the number is prime. Otherwise, it will return False. First checking with 7 and then with 8.

Example:

def isprime(num): if num==2 or num==3: return True if num%2==0 or num
This method is implemented using function. It will return True if the number is prime. Otherwise, it will return False. First checking with 13 and then with 18.
Example:
def isprime(num): if num == 2 or num == 3: return True if num < 2 or num%2 == 0: return False if num < 9: return True if num%3 == 0: return False a = int(num**0.5) b = 5 while b 
This method is implemented using function. It will return True if the number is prime. Otherwise, it will return False. First checking with 15 and then with 2.
Example:
def isprime(num): if num> 1: for n in range(2,num): if (num % n) == 0: return False return True else: return False print(isprime(64)) print(isprime(5))
 
This method is implemented using function. It will return True if the number is prime. Otherwise, it will return False—first checking with 64 and then with 5.
 
2: Using if-else statements
 
n=int(input("Enter a number:")) if n>1: for i in range(2,n//2): if(n%i)==0: print(n,"is not a prime number") break else: print(n,"is a prime number") else: print(n,"is neither prime nor composite")
 
This code is normally using loops. Here we are getting a number as an input from the user. It performs the code and gives the result to the user. If the user gives 1 as an input, it will display neither prime nor composite.
 
Enter a number:14 14 is not a prime number Enter a number:3 3 is a prime number Enter a number:1 1 is neither prime nor composite
 
3: Using math function to check if number is prime python
 
Math is a module that is already available in the python library. This module contains a lot of mathematical functions. To access this module, we have to import the module as:
 
Here we are using math.sqrt to check if the number is prime or not. sqrt() is a built-in function in python.
 
Syntax
 
Parameter
 
x – that can be any value.
 
Returns
 
It returns the square root of the x value.
 
Code
 
import math def isprime(num): a=2 while a1 print(isprime(14)) print(isprime(7))
 
4: Using sympy module
 
Sympy is a module in the python library. It only depends on mpmath. Here we are simply using a sympy module. The pip command line to install the module is:
 
Syntax
 
Parameter
 
Returns
 
Example:
 
import sympy print(sympy.isprime(90))
 
Example:
 
from sympy import * print(isprime(19))
 
Example:
 
import sympy.ntheory as nt print(nt.isprime(8))
 
5: Using primePy library to check if a number is prime or not
 
The primePy is a library that is useful to perform the operations regarding prime numbers. Here we are using primePy to check whether a number is prime or not. The pip command to install the primePy module:
 
Syntax
 
Parameter
 
Returns
 
Code
 
from primePy import primes print(primes.check(63))
 
6: Using is_integer function
 
 is_integer is a built-in function that is useful to check if the given number is an integer or not. It is also useful to check if it is prime or not.
 
Syntax
 
Parameter
 
Returns
 
Boolean values (True or False)
 
Example:
 
def prime(num): a=[] for i in range (1, num+1): if (num/i).is_integer(): a.append(i) if len(a)==2: print("Prime") else: print("Not Prime") prime(2)
 
Learn Something New: How to generate a random prime number?
 
import random def range_primes(a, b): prime = [] for i in range(a, b): is_prime = True for n in range(2, i): if i % n == 0: is_prime = False if is_prime: prime.append(i) return prime prime= range_primes(1,100) random_prime = random.choice(prime) print("Random Prime Number is:", random_prime)
 
Random Prime Number is: 11
 
Check if Number is Prime Using Recursion
 
You can check for all prime numbers using the Prime function. Simply pass the number as th3 argument.
 
i=2 def Prime(no, i): if no == i: return True elif no % i == 0: return False return Prime(no, i + 1)
 
Here, we will recursively call the Prime function to check if the number is prime.
 
FAQs Related to Check If a Number is Prime or Not in Python
 
Prime numbers are the numbers that are not the product of any other numbers. These numbers are always natural numbers.
 
To check if a number is prime or not. We have to create a for loop to iterate the numbers. Suppose the number is greater than one. It will check whether a number is a product of any number. If it is, it displays False as a result.
 
Conclusion
 
Here we have briefly learned about how to check if a number is prime or not. We have learned many possible ways. With that, we also saw how to generate a prime number. We hope this article is helpful. Try to solve the programs on your own to gain more knowledge.
 
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Prime Numbers in Python
 
 
A Prime number can be explained as a finite number that is only divisible by 1 and by itself. It goes on like 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, etc. This series of numbers can be recreated, and any given number can be identified if it is a prime number or not by implementing the logic in the python programming language. A few of the ways for this operation are using python libraries, coding with while loops, coding with loops and conditions, and using the lambda function.
 
Web development, programming languages, Software testing & others
 
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 etc.
 
Techniques to Implement Prime Number in Python
 
Prime numbers can be implemented in python by several techniques; four among them are explained below:
 
1. Using Lambda Function
 
# Prime determination method def Prime_series(number): for iter in range(2,number): if is_prime(iter) == True: print(iter,end = " ") else: pass number = int(input("Enter the input Range : ")) is_prime = lambda number: all( number%i != 0 for i in range(2, int(number**.5)+1) ) Prime_series(number) 
 
 
Explanation: This program determines the range of prime numbers using the lambda function technique; lambda represents an anonymous function or an orphan function. The program executes in such a manner that once a specific integer is keyed in by the user, then all the prime numbers within the range of 2 to key in the input will be generated and displayed.
 
Program Flow:
 
 
The input range is keyed in by the user; the python input function is used to receive the user’s input. The received input is handily cast into INT type.
 
The casted input is passed as an argument in a function call process. This function is responsible for triggering the lambda function for each and every integer in the given range of 2 to key in the input.
 
Hence the lambda function is called for each and every integer, and a prime check is carried on; the below-formulated logic is used for attaining this prime check, number%2 != 0
 
 
So as per the above-formulated logic, a Boolean value will be returned; the next step for each verified integer in the function is to check whether the returned Boolean is true or false, in the case when it falls true, then the corresponding variable is printed in the console.
 
2. Using for Loops and Conditions
 
# Prime determination method number = int(input("Enter the input Range : ")) for iter in range(2,number): for i in range(2,iter): if (iter%i==0): break else: print(iter) 
 
 
Explanation: This program determines the range of prime numbers using for loops and conditions; the program executes in such a manner that once a specific integer is keyed in by the user, then all the prime numbers within the range of 2 to keyed in input value will be generated and displayed.
 
Program Flow:
 
 
The input range is keyed in by the user; the python input function is used to receive the user’s input. The received input is handily casted into INT type.
 
Here, a nested loop is used to determine two integers; the first loop ensures to retrieve all the elements or integers falling within the range keyed. The second for-loop is responsible for determining the denominator of the prime check.
 
For every integer value denominated, if the outcome of the process is not equal to zero, then the integer handled is printed to the console.
 
This process is looped on and executed for every integer in the mentioned range of 2 to keyed in the input.
 
 
3. Using While Loops
 
range = int(input('Enter the integer range to find prime no: ')) number = 1 while(number 
 
 
Explanation: This program determines the range of prime numbers using while loops and conditions; the program executes in such a manner that once a specific integer is keyed in by the user, then all the prime numbers within the range of 2 to the keyed in the input will be generated and displayed.
 
Program Flow:
 
 
The input range is keyed in by the user; the python input function is used to receive the user’s input. The received input is handily casted into INT type.
 
Here a while loop is used for the prime check; the loop control is designed on a condition check where the looping process will be happening until the input value is greater than the loop control variable. Notable, the loop control variable is initiated with 1 and incremented by 1 on each and every looping.
 
Here again, for every integer value denominated in the process’s outcome equal to zero, then the integer handled is printed as ” Not a prime number”; otherwise wise it is printed as ” Prime Number.”
 
This process is looped on and executed for every integer in the mentioned range of 1 to a keyed input value.
 
 
4. Using Python Libraries
 
import sympy start = int(input( " starting value : " )) end = int(input( " ending value : " )) list_prime_values = list(sympy.primerange(start,end+1)) print("All prime values in the range : " , list_prime_values)
 
 
Explanation: This program determines the range of prime numbers using predefined libraries; here, the sympy library is used for attaining the prime check; the program flow is designed to expect the starting and ending range for the determination of prime numbers.
 
Program Flow:
 
 
The starting and ending range is keyed in by the user; the python input function is used for receiving the input from the user. The received input is handily casted into INT type.
 
The keyed-in start and end range are passed as input to the prime range function of the sympy library. The output of the function is casted into a list variable, and then it printed.
 
 
Recommended Articles
 
This is a guide to the Prime Numbers in Python. Here we discuss the basic concept and techniques to implement prime numbers in python. You may also look at the following articles to learn more –
 
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