[Tutor] Program to find if a number entered by user is a prime number or not

[Mark Lawrence]

On 16/10/2020 02:49, Manprit Singh wrote:

[fix extremely irritating top posting]

> On Fri, Oct 16, 2020 at 7:00 AM Manprit Singh <manpritsinghece at gmail.com>
> wrote:
> 
>> Dear Sir ,
>>
>> I was trying to write a program which allows the user to input a number
>> from a keyboard , it then prints the message x is prime if number input by
>> user is a prime number and x is not prime if the number input by user is
>> not a prime number. (here x represents the number). The program is written
>> below:
>>
>> x = int(input("Enter any positive number"))
>> a = "not prime"
>> if all(x%i for i in range(2, int(x**0.5) + 1)):
>>      if x < 2:
>>          pass
>>      else:
>>          a = "prime"
>> else:
>>      pass
>> print(x,"is",a)
>>
>> I have these questions in my mind :
>> 1) If you can see I have used pass two times , Initially I have assigned a
>> string "not prime" to variable a . Now if user input is either 0 or 1 , it
>> is not a prime number. That's why i have written a pass inside the below
>> written block, which will  maintain a = 'not prime" when user input is
>> either 0 or 1.
>>
>> if all(x%i for i in range(2, int(x**0.5) + 1)):
>>      if x < 2:
>>          pass
>> for any value of user input greater than 1 if the iterable inside all( )
>> is empty or all(x%i for i in range(2, int(x**0.5) + 1)) return True , the
>> user input for sure is a prime number , and hence i have assigned a =
>> "prime" inside that block.
>>
>> Again for the second time i have used pass when all(x%i for i in range(2,
>> int(x**0.5) + 1)) returns False, in that case the number input by user is
>> again not a prime number , and hence i have used pass again in the block to
>> maintain the old value of variable a ="not prime".
>>
>> Just need to know if my way of implementing the problem is correct ? Can
>> this program be further optimised ?
>>
>> Regards
>> Manprit Singh
>>

 > Dear sir,
 > If i simply write this program as given below:
 >
 > x = int(input("Enter any positive number"))
 > a = "not prime"
 > if all(x%i for i in range(2, int(x**0.5) + 1)):
 >      if x >= 2:
 >          a = "prime"
 > print(x,"is",a)
 >
 > Will it be ok ?
 >

If you have tested it yes it will be ok.

-- 
My fellow Pythonistas, ask not what our language can do for you, ask
what you can do for our language.

Mark Lawrence