## How the Prime number code in python works?

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def is_prime(num): for i in range(2,num): if (num % i) == 0: return False return True def all_primes(num): primes = [] for n in range(2,num+1): if is_prime(n) is True: primes.append(n) return primes num = int(input("Enter upper limit: ")) primes = all_primes(num) print(primes)

How does it happens... What understand is if I enter 10 It will be 10%2= 5...the remainder is 0 so it skip to the next one 9%2 = True there is remainder.

It moves to the next one 9%3 remainder is 0 so it skips to 8% ...,then 7 .......but what I dont understand is 7 if it's check until 7%7 ==0 then how did it add 7 as Prime number???

I'm so confused.

Thank you for any comment

but what I dont understand is 7 if it's check until 7%7 ==0

The `range`

*function* from the following line:

for i in range(2, num):

goes from `2`

to `num - 1`

.

So, the `range()`

*function* doesn't include the last (stop) number in the result.

**Python Program to Check Prime Number,** Source code to print all prime numbers between two numbers enterd by user in Python programming with output and explanation Is 2 prime: True Is 4 prime: False Is 7 prime: True Method-2 In this method, we are reducing the number of iterations by cutting them to the square root of n.Let's see the code.

You got it wrong. If you enter `10`

, it wouln't check `10%2`

and then `9%2`

...

It would check `10%2`

, then `10%3`

, then `10%4`

... i.e. it would check `10%i`

, for `i`

ranging from `2`

to `9`

. However, note that execution in `is_prime`

stops as soon as the remainder is 0:

for i in range(2,num): if (num % i) == 0: return False

So if `num`

is `10`

, only `10%2`

would be checked, and since it's `0`

, it would immediately return `false`

.

If `num`

is `9`

, for example, it would check `9%2`

. Since the remainder is not `0`

, it would move up to checking `9%3`

. The remainder is `0`

there, so it would return `false`

in that case.

If `num`

was `7`

, it would check `7%2`

. The remainder is not `0`

so it checks `7%3`

, which is also different from `0`

, and so on. The last check performed would be `7%6`

, because `for i in range(2,num)`

means that it will iterate with `i`

ranging from `2`

to `num-1`

. In this case, `is_prime(7)`

would return `true`

because `7%i`

, with `i`

ranging from `2`

to `6`

is different than `0`

.

**Python Program to Print all Prime Numbers in an Interval,** Given a positive integer N. The task is to write a Python program to check if the number is prime or not. Definition: A prime number is a natural� A prime number is the one that is not divisible by any other number except 1 and itself. In Python % modulo operator is available to test if a number is divisible by other. Assuming we have to find prime numbers between 1 to 100, each number (let us say x) in the range needs to be successively checked for divisibility by 2 to x-1.

when `is_prime`

is called for number `7`

, the loop will run from `2`

to `6`

only. Hence `7%7`

will never be checked , returning True for such case.

**Python program to check whether a number is Prime or not ,** In this post, we will write a program in Python to check whether the input number is prime or not. A number is said to be prime if it is only divisible by. The numbers 2, 3, 5, 7, etc. are prime numbers as they do not have any other factors. To find a prime number in Python, you have to iterate the value from start to end using a for loop and for every number, if it is greater than 1, check if it divides n. If we find any other number which divides, print that value.

A prime number, by definition, is a number that is divisible only by itself and 1.

Therefore, your function `is_prime`

gets the number you want to check if it is prime, and try to find any other number that can divide it inside the interval [2, num), this interval is implemented using the function `range(2,num)`

inside the for loop.

If it finds any case, i.e., if the `if (num % i) == 0`

is satisfied, we know that there is a number which divides it, therefore, by definition it is not a prime number.
After checking the whole list, if you cannot find a divisor, we can say that the number is prime, i.e., the `return True`

on your function.

Example: You want to check 9 (1st step) num = 9, i = 2. 9%2 != 0, we continue in the loop with next value of i. (2nd step) num = 9, i = 3. 9%3 == 0, we return False. As we know, 9 can divide by 3. Another example: You want to check 7 num = 7, i = 2 7%2 != 0, so we continue in the loop with the next value of i num = 7, i = 3 7%3 != 0, so we continue in the loop with the next value of i num = 7, i = 4 7%4 != 0, so we continue in the loop with the next value of i num = 7, i = 5 7%5 != 0, so we continue in the loop with the next value of i num = 7, i = 6 7%6 != 0, so we continue in the loop with the next value of i The if was never fulfilled, therefore we reach the end of the loop and call the next command, which is return True.

**Python Program to Check If a number is Prime or not,** 2 does not work with this code even though it is a prime number. Like � Reply � Mark as spam � 36w. Python Program to Check Prime Number. A prime number is a natural number greater than 1 and having no positive divisor other than 1 and itself. For example: 3, 7, 11 etc are prime numbers. Other natural numbers that are not prime numbers are called composite numbers. For example: 4, 6, 9 etc. are composite numbers.

**How to Test for Prime Numbers in Python,** How the Program Works. primeSieve.py. 1. # Prime Number Sieve. 2. # http:// inventwithpython.com/hacking (BSD Licensed). 3. 4. import math. The only module� To find a prime number in Python, we can have to create a special function solely for this purpose. There is no built-in function in Python for this purpose. By definition, a prime number is a natural integer number which is greater than 1 and has no positive divisors other than 1 and itself. In other words an integer number only divisible by 1 and itself.

**Finding Prime Numbers,** we use Python to identify prime numbers. This is important in cryptography and number Duration: 6:02
Posted: Jun 28, 2017 If we find any number that divides, we return false. If we did not find any number between 2 and N/2 which divides N then it means that N is prime and we will return True. Below is the Python program to check if a number is prime: filter_none. edit.

**Python and Prime Numbers || Python Tutorial || Learn Python ,** Add a break once you find prime to exit the while loop. Making only minimal changes to your code to make it work: a=2 num=� Python for Loop. Python break and continue. A positive integer greater than 1 which has no other factors except 1 and the number itself is called a prime number. 2, 3, 5, 7 etc. are prime numbers as they do not have any other factors. But 6 is not prime (it is composite) since, 2 x 3 = 6.

**Python Prime number checker,** Below is a simple function to check for a prime number. Next, execute the is- prime-number.py python script to search for a prime Subscribe to Linux Career NEWSLETTER and receive latest Linux news, jobs, career� when I enter a prime number it works but when I enter a non prime number it doesn't work. to fix your code, examples/prime-number # Python program to check if