In this post, you will learn a python program to check given number is prime or not but before writing a program we should know what is a prime number.

## What is prime number?

A number that is only divisible by 1 and itself is known as a prime number. An example of a prime number is 2,3,5,7,11,13,17,19… etc.

we should write this program in three different ways:

- Simple way (By taking user input).
- by using function.
- Except error if user enter wrong input.

## 1. Simple way (By taking user input)

Write a python program to check given number is prime or not by taking user input.

Before writing this program you should know about:

**Source Code**

```
num = int(input("enter a number to check entered number is prime or no :"))
p = 0
print(f"{num} is divide by :",end=" ")
for i in range(2,num):
if num%i==0:
print(i, end=",")
p=1
print("\t")
if p==1 and num!=2:
print(f"{num} is not a prime number")
else:
print(f"{num} is a prime number")
```

**Output-1**

```
enter a number to check entered number is prime or no :4
4 is divide by : 2,
4 is not a prime number
```

**Output-2**

```
enter a number to check entered number is prime or no :2
2 is divide by :
2 is a prime number
```

### Explanation

** num** variable is used to take integer value as input from the user.

** p** variable (which is initially

**) is used to check for prime numbers when**

`0`

**which means that**

`p=1`

**is not a prime number.**

`num`

with the help of** for loop **and

**if statement**

we check for **is divisible by any other number (Except 1 or**

`num`

**) or not, if a number is divisible by any other number then**

`num`

**that shows**

`p=1`

**is not a prime number.**

`num`

## 2. prime number By using function

Write python program to check given number is prime or not using function.

Before writing this program you should know about:

**Source Code**

```
def prime_number(n):
check_prime = 0
for i in range(2,n):
if n%i == 0:
check_prime = 1
if check_prime == 1:
return f'{n} is not a prime number'
else:
return f'{n} is a prime number'
# you can also take user input instead of writing direct value
# user input - demo
# num1 = int(input("ENter a number: "))
# prime_number(num1)
print(prime_number(2))
print(prime_number(4))
print(prime_number(5))
print(prime_number(6))
print(prime_number(7))
print(prime_number(9))
```

**Output**

```
2 is a prime number
4 is not a prime number
5 is a prime number
6 is not a prime number
7 is a prime number
9 is not a prime number
```

## 3. Except error if user enter wrong input.

Write a python program to check given number is prime number or not and also handle exception if user input wrong data.

before writing this program you should know about:

**Source code**

```
def prime_number(n):
check_prime = 0
for i in range(2,n):
if n%i == 0:
check_prime = 1
if check_prime == 1:
return f'{n} is not a prime number'
else:
return f'{n} is a prime number'
while True:
try:
number = int(input("Enter a number: "))
if type(number) == int:
break
except ValueError:
print("please enter number only")
print(prime_number(number))
```

**Output-1**

```
Enter a number: seven
please enter number only
Enter a number: 7
7 is a prime number
```

**Output-2**

```
Enter a number: four
please enter number only
Enter a number: 4
4 is not a prime number
```

Hope this post help you and add good value to your life -thank you.

## 1 Comment

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