Python Program To Check Prime Number

# Python Program To Check Prime Number

Last updated:
15th Jun, 2023
Views
8 Mins
View All

Python programming is one of the most popular programming languages that is used in the latest technology. A beginner in any programming languages would have come across initial practice exercises such as identifying prime numbers, even or odd numbers, etc. In this article, we will learn how to write a prime number program in Python to check whether a number entered by the user is a prime number or not.

To write this program, firstly, we need to understand what a prime number is. A prime number is a natural number that is only divisible by 1 and itself, which means that this number cannot be a product of any other smaller two numbers. For example, 2, 3, 7, 11, 13, 17, etc. are prime numbers.

The program has to check if the number is divisible by any of the numbers lying in between 2 and itself. If it is divisible by any of these numbers, the remainder will be zero, and we can conclude that it is not a prime number. And if the remainder is not zero, then it is a prime number.

## Python Programming Topics

There are three Python programming topics that one should know to be able to write the prime number program in Python. These are:

### 1. If…else statement

This is used when there is a need to decide whether to execute a particular set of codes or no. It depends on the condition. If the condition is satisfied, i.e., the test expression is true, then the statements will be executed. If the condition is not satisfied, the statements will not be executed, and it will jump to the ‘else’ section of the code.

```if test expression:

Body inside if

else:

Body inside else

A simple example better explains this:

#To check if the number is positive and print accordingly

num = 5

if num > 0

print(“Number is Positive)

else

print(“Number is Negative)

Output: Number is positive```

### 2. For Loop

The For loop is used to iterate over a sequence. So, for each item in the list or set, a set of statements can be executed.

```for variable in sequence:

Body inside for

For example:

sports = [“cricket”, “football”, “tennis”]

for z in sports:

print(z)

Output: cricket

football

tennis```

### 3. Break

The break statement can change the flow of a loop in Python. Usually, a loop repeats over a sequence of codes continuously till the condition is not satisfied or the test expression is false. But sometimes, we may want to stop the current iteration of a loop or maybe the whole loop by checking for one condition. In such cases, a break statement is used.

```for variable in sequence:

if condition:

break

The loop will be broken once the condition is satisfied.

To understand better with an example:

for var in “mango”:

if var == “g”:

break

print(var)

Output: m

a

n```

upGrad’s Exclusive Data Science Webinar for you –

Watch our Webinar on How to Build Digital & Data Mindset?

## Prime Number Program In Python

In this program, we will first ask the user to enter a number. After that, we will check if the number is greater than 1. If it is, we will check if it is divisible by any number between 2 and itself. If it is divisible, then it prints that the number is not a prime number. If it is not divisible, then it prints that the number is a prime number. And if the number is less than 1, then it prints that the number is not a prime number.

The Python program is as follows:

```num = int(input("Enter a number: "))

if num > 1:

for i in range(2, num):

if (num % i) == 0:

print(num, "is not a prime number")

break

else:

print(num, "is a prime number")

else:

print(num, "is not a prime number")

Explore our Popular Data Science Online Courses

Executive Post Graduate Programme in Data Science from IIITB
Professional Certificate Program in Data Science for Business Decision Making
Master of Science in Data Science from University of Arizona
Advanced Certificate Programme in Data Science from IIITB
Professional Certificate Program in Data Science and Business Analytics from University of Maryland
Data Science Online Courses

```

The int() statement is used to convert any number entered by the user into an integer. The range() statement is used so that the value of “i” goes through each number from 2 to the number entered by the user. The print() statement is used to print the value inside the bracket into the output. The user can now check whether any number entered by them is a prime number or no.

## Read our popular Data Science Articles

 Data Science Career Path: A Comprehensive Career Guide Data Science Career Growth: The Future of Work is here Why is Data Science Important? 8 Ways Data Science Brings Value to the Business Relevance of Data Science for Managers The Ultimate Data Science Cheat Sheet Every Data Scientists Should Have Top 6 Reasons Why You Should Become a Data Scientist A Day in the Life of Data Scientist: What do they do? Myth Busted: Data Science doesn’t need Coding Business Intelligence vs Data Science: What are the differences?

## Top Data Science Skills to Learn to upskill

 SL. No Top Data Science Skills to Learn 1 Data Analysis Online Courses Inferential Statistics Online Courses 2 Hypothesis Testing Online Courses Logistic Regression Online Courses 3 Linear Regression Courses Linear Algebra for Analysis Online Courses

## The Sieve of Eratosthenes Algorithm

There is an antique set of rules for figuring out high numbers up to a selected size called the Sieve of Eratosthenes. The algorithm generates a list of numbers up to a given limit and then repeatedly notes multiples of each prime until there is no more prime no in Python. The remaining unsigned numbers are all primes.

The Sieve of Eratosthenes Algorithm is the Python program to check prime number.

```def sieve_of_eratosthenes(limit):

primes = [True] * (limit+1)

p = 2

while p**2 <= limit:

if primes[p]:

for i in range(p**2, limit+1, p):

primes[i] = False

p += 1

return [i for i in range(2, limit+1) if primes[i]]

```

A “break” statement in an internal loop is any other optimization technique for verifying primes. There is a vintage set of rules for figuring out top numbers as much as a specific size called the Sieve of Eratosthenes. Instead of repeatedly iterating over all the numbers up to a certain restriction, we may also stop the loop as quickly as we find an issue of the wide variety. A Python Function using the “break” Command

```def is_prime(n):

if n <= 1:

return False

for i in range(2, int(n**0.5)+1):

if n % i == 0:

return False

break

return True```

## The Difference between “is” and “==” Operators in Python

The “is”; operator determines if variables have an equal price, while the Python &quot;is&quot; operator determines whether variables are a part of the identical memory item. Whether we use the “is” or “==”; the operator would not surely rely whilst evaluating variables to integers or other immutable sorts. On the other hand, the  “is”; operator might also yield surprising outcomes for changeable kinds like dictionaries or lists. It is also a Python program to print prime numbers.

Here is an instance:

```a = [1, 2, 3]

b = [1, 2, 3]

print(a == b)   # True

print(a is b)   # False

```

Recursive Functions to Check Prime Numbers

A recursive function repeatedly calls itself until it hits the main character. An integer’s primeness can be checked using a recursive function. Here is the Prime no program in Python

```def is_prime(n, i=2):

if n <= 2:

return True if n == 2 else False

if n % i == 0:

return False

if i**2 > n:

return True

return is_prime(n, i+1)```

## Miller-Rabin Algorithm

The Miller-Rabin algorithm, a probabilistic algorithm, is the Python program to find prime number. The algorithm chooses a random witness number and checks that it meets certain conditions. The probability that the algorithm gives a wrong result can be arbitrarily small by choosing enough witnesses.

Here is a Python implementation of the Miller-Rabin algorithm:

```import random

def is_prime(n, k=5):

if n <= 3:

return n == 2 or n == 3

if n % 2 == 0:

return False

# write n-1 as 2^s * d

s, d = 0, n-1

while d % 2 == 0:

s += 1

d //= 2

# perform k rounds of testing

for _ in range(k):

a = random.randint(2, n-2)

x = pow(a, d, n)

if x == 1 or x == n-1:

continue

for _ in range(s-1):

x = pow(x, 2, n)

if x == n-1:

break

else:

return False

return True```

## Conclusion

This article demonstrates how to write a simple program for a prime number in Python language. Using this logic, we can write other basic programs to improve our skills. And we have also learned three programming topics, i.e., if..else statement, for loop, and break. These are basic topics that can be used for more complicated and long programs to execute larger tasks to understand a prime number in Python.

Check out all trending Python tutorial concepts in 2024.

If you are curious about learning data science to be in the front of fast-paced technological advancements, check out upGrad & IIIT-B’s Executive PG Programme in Data Science and upskill yourself for the future.

#### Rohit Sharma

Blog Author
Rohit Sharma is the Program Director for the UpGrad-IIIT Bangalore, PG Diploma Data Analytics Program.
Get Free Consultation

Select
Select Area of interest
Select Work Experience
By clicking 'Submit' you Agree to

#### Data Science Skills to Master

1What are Python's distinct features?

Python is a well-known programming language among data scientists and Machine Learning experts. Python's success stems because it is easy to learn and has a simple syntax and readability. It is easy to comprehend, making troubleshooting simple.

Also, it is a free and open-source programming language, and Python Professionals can use it in a variety of ways. It is an object-oriented language that supports class notions, and it is simple to combine with other languages such as C++, Java, and others.

2What are functions in Python?

Functions are pieces or parts of a Python code that are organized and reused to execute single and related actions. Functions are helpful in improving modularity in systems that reuse a significant degree of code. Python has a variety of built-in functions, such as print(). Along with providing a wide range of built-in functions, Python also allows you to build user-defined functions.

3What are the real-life use cases of Python?

Python is one of the world's most widespread programming languages today. Most of the computational and software programs employ Python for their core programming requirements. It includes surfing Google, going through Instagram, watching videos on YouTube, or listening to music on Spotify. All of these activities are directly or indirectly related to Python. This shows that Python is utilized on a wide range of platforms, applications, and services.

## Suggested Blogs

66143
In my journey through data structures, I’ve navigated the nuances of linear search vs binary search in data structure, especially when dealing w

23 Jun 2024

64450
An Information Retrieval System is a set of algorithms that facilitate the relevance of displayed documents to searched queries. In simple words, it w

18 Jun 2024

61761
In this article, you will learn about the Types of Trees in Data Structures with examples, Properties & Applications. In my journey with data stru

31 May 2024

40594
The communication network is expanding, and so the people are using the internet! Businesses are going digital for efficient management. The data gene

29 May 2024

54956
Data structures are the data structured in a way for efficient use by the users. As the computer program relies hugely on the data and also requires a

28 May 2024

318837
Summary: In this Article, you will learn about what are the 4 Types of Data in Statistics. Qualitative Data Type Nominal Ordinal Quantitative Data

28 May 2024

909244
Wondering what is the range of Python developer salary in India? Before going deep into that, do you know why Python is so popular now? Python has be

by Sriram

21 May 2024

89686
Data structures serve as the backbone of efficient data organization and management within computer systems. They play a pivotal role in computer algo