Here you will get python program to check prime number.
A number is called prime number if it is only divisible by 1 or itself. For example 2, 3, 5, 7, 11, etc are prime numbers.
Below program takes a number as input and checks it is prime number or not.
Python Program to Check Prime Number
num = int(input("enter a number: "))
for i in range(2, num):
if num % i == 0:
print("not prime number")
break
else:
print("prime number")
Output
enter a number: 11
prime number
Video Tutorial
Comment below if you have any queries related to above python prime number program.
Here according to the program else is inside the for loop. When the if condition fails, directly it will print as the number is not prime until checking up to the last value. If I take num=9, then in first iteration (9%2)==0 (false) else statement will be executed. But 9 is not prime right. can u explain me this prgm.
See, this else is not the part of if. In python for loop is little different from other languages like C and C++. In python we can use a else statement with for loop. After the loop ends, else statement is executed. In case break is used somewhere in loop then else is not executed. The program is correct and works fine, just try to run it.
You can learn about for loop in python here https://www.programiz.com/python-programming/for-loop
No it is itterating program is wrong
you are foolish
You are foolish , just go and run it you will come to know that its correct and if it would be wrong too just have etiquettes to say it wrong . This is not the way to abuse anyone , any human can commit mistakes and after all , he is only helping us . JUST BEHAVE PROPERLY.
if we are checking with the number 2, this condition becomes true ( if num % i == 0:)
2%2==0. Then why it is going to the else statement?
It won’t do because how can you find range between 2 and 2
def prime_check(number= ‘Plese enter a valid number’):
for s in range(2,number+1):
if number<=1 or number / s != 0:
print("it's not a prime number")
else:
print("It's a prime number")
return
Sir I can check as below also.
I am mentioning the logic here only
initialize i to 2
Store the number to be checked at n
now I will check for every i that whether it divides n or not;and the loop will continue till i reaches n
if for any value of i it divides n,n will be non-prime and if no value of i can divide n then n will be prime.
Sir I cannot fully apply the idea in my program.Will you please help me ASAP?
sir ur program gives an error while we entering greater than 10 .this error only occur when we enter prime number ..
thanks brother , my program doesn’t runs because i doesn’t put the break statement at end of loop.
for i in range(2,30):
j=2
while j<i:
if i%j==0:
j=j+1
break
else:
print("%s it is prime"%(i))
j=j+1
break
def primes(num):
list=[]
for i in range (2,int(num/2)+1):
if ((num%i)==0):
break
else:
list.append(i)
return list
primes(11)
iam unable to append primes to list please help me out
It returns a list of primes upto a number n.
def primes_upto(n):
arr = []
for i in range(1, n+1):
if i in [2, 3]:
arr.append(i)
continue
for j in range (2, (i//2) + 1):
if i % j == 0:
break
if j == i//2:
arr.append(i)
return arr
This program has a small error. This works fine for other inputs except for 4. It says 4 is a prime number which is actually not.
When input is 4, range function is range(2, 2). This returns an empty list. Thus the execution is jumped to else block. And, it prints ‘prime number’.
Hence, it should be range(2, int(n/2) + 1) instead of range(2, int(num/2)).
This corrects the error!
Thanks for pointing out mistake, I have corrected it.
When the chosen number is 2, how does it not print anything from the if statement when 2%2 is 0. I am confused.
As the function range(2,var) will produce list of numbers from 2 up to var.i.e. 1 less than var. so in the case var=2,
range(2,2) produces EMPTY LIST. And thus 2 never gets break statement.
1 is not a prime but this program never considered that.
I really like your code because its very simple and easy to understand.
Sir your program is wrong we check 2 is prime or not they give me 2 is not prime number
I want given number is palindrome or not program by using if conditions only don’t use while condition to write that program on python
#this code prints prime number according to your limit
def primenumber(limit):
for j in range (2,limit):
for i in range(2,j):
if j%i == 0 :
break
else:
print(j)
x=int(input(“enter the limit: “))
primenumber(x)
# taking input from user
number = int(input(“Enter any number: “))
# prime number is always greater than 1
if number > 1:
for i in range(2, number):
if (number % i) == 0:
print(number, “is not a prime number”)
break
else:
print(number, “is a prime number”)
# if the entered number is less than or equal to 1
# then it is not prime number
else:
print(number, “is not a prime number”)
import math
a = int(input(‘enter a positive number’))
def checkprime(num):
for i in range(2,int(math.sqrt(num))):
if(num % i == 0):
print(“not prime”)
break
else:
print(“prime number”)
return “prime”
b = checkprime(a)
sir,if we take the number as 2 then it will display as not prime number,but it is prime .
Typing mistake(excluded some lines in the previous one)
This is the corrected one:
x=eval(input (“enter number: “))
a=[]
for i in range(1,x+1):
if x%i==0:
a.append(i)
if x in range(2,x+1) and len(a)=2:
print(“The number is composite.”)
elif x in range(0,2):
print(x,”is neither prime nor composite.”)
x=eval(input (“enter number: “))
a=[]
for i in range(1,x+1):
if x%i==0:
a.append(i)
if x in range(2,x+1) and len(a)=2:
print(“The number is composite.”)
elif x in range(0,2):
print(x,”is neither prime nor composite.”)
#This is my unique self designed code which is fully functional.