Any tips?

Language Help Python
1

hi guys.
i’m a little stuck, any tips?

labdcsvaLB
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Prime Number Finder: Prime Number Finder | Codecademy

2

scrn1

The challenge isn’t placing any maximum value restriction on n.

Here are a few things to consider:

  • Suppose the argument to the function is 6, then the expected result should be [2, 3, 5] whereas your function will return [2, 3, 5, 7]. This contradicts the challenge specification “… and returns all the prime numbers from 1 to n (inclusive)”. Your function doesn’t work properly when the provided argument is in the range 1 to 6 as your function is returning extra prime numbers.

  • You are deciding whether a number is prime or not by checking its divisibility by the numbers 2, 3, 5 and 7. That approach will work when the provided argument is about 100. But for numbers greater than 100, you can’t just rely on divisibility by 2, 3, 5 and 7.
    For Example, if the argument to the function is 121, then 121 is included in your list of primes. But 121 is most certainly not a prime number (11 x 11 = 121) because the factors of 121 are 1, 11, 121. You could tack on

and num % 11 != 0

to your if condition. But, what happens if the provided argument is 169? Your function would identify 169 as a prime number even though it is not (since 13 x 13 = 169).
You can’t write an if condition with a finite number of possibilities beforehand which exhaustively guarantees that your function will work for all n.

Your if condition will work up to a certain point and then it won’t. Manually tacking on more operands after the and is not going to solve the underlying issue. You need to re-think your approach.

3

that’s a really interesting perspective , but how to fix it?