Validating given input and printing every prime number =< given input. (Python)
Question:
So I have read tons of solutions to this type of questions, but they all seem to be way too complicated, or I can’t find any useful solutions in them.
I have written the first part where I have to ask for an input and validate it to be an integer, but I can’t figure out how to write the code for the second part. Efficiency isn’t a necessity here, but I think it’s better if I learn the most efficient way from the get go. From what I read, using the radicle of the input and checking the divisors is the way to go here, but as I said, I can’t figure out how to actually write the code and integrate it into what I already have.
while True:
x = str(input("Please enter an integer: "))
try:
x = int(x)
except ValueError:
print("Please enter a valid integer: ")
continue
break
Any help is greatly appreciated!
Answers:
Write an isPrime(n) function that returns true if n is prime, false otherwise. Then test all the numbers from 2 up to the entered integer to see if they are prime.
We will help you to improve your code, but you have to write it first.
It is better to edit multi-line code into your question, rather than post a comment, because then you are not limited to a single line.
Your code appears to be:
def is_prime2(n):
if n == 2 or n == 3:
return True
#endif
if n % 2 == 0 or n < 2:
return False
#endif
for i in range(3, int(n**0.5)+1, 2):
if n % i == 0:
return False
#endif
#endfor
return True
#enddef
print(n)
I have added comments to indicate where I think that various statements end. I may have mistaken the indentation converting from a single line.
Apart from that print(n), which is either not part of the function definition or comes after a return, this appears to work correctly. It will be too slow for very large values of n though it will be fine for smaller values and for testing. For very large values have a look at the Sieve of Eratosthenes.
So I have read tons of solutions to this type of questions, but they all seem to be way too complicated, or I can’t find any useful solutions in them.
I have written the first part where I have to ask for an input and validate it to be an integer, but I can’t figure out how to write the code for the second part. Efficiency isn’t a necessity here, but I think it’s better if I learn the most efficient way from the get go. From what I read, using the radicle of the input and checking the divisors is the way to go here, but as I said, I can’t figure out how to actually write the code and integrate it into what I already have.
while True:
x = str(input("Please enter an integer: "))
try:
x = int(x)
except ValueError:
print("Please enter a valid integer: ")
continue
break
Any help is greatly appreciated!
Write an isPrime(n) function that returns true if n is prime, false otherwise. Then test all the numbers from 2 up to the entered integer to see if they are prime.
We will help you to improve your code, but you have to write it first.
It is better to edit multi-line code into your question, rather than post a comment, because then you are not limited to a single line.
Your code appears to be:
def is_prime2(n):
if n == 2 or n == 3:
return True
#endif
if n % 2 == 0 or n < 2:
return False
#endif
for i in range(3, int(n**0.5)+1, 2):
if n % i == 0:
return False
#endif
#endfor
return True
#enddef
print(n)
I have added comments to indicate where I think that various statements end. I may have mistaken the indentation converting from a single line.
Apart from that print(n), which is either not part of the function definition or comes after a return, this appears to work correctly. It will be too slow for very large values of n though it will be fine for smaller values and for testing. For very large values have a look at the Sieve of Eratosthenes.