Question

I am just starting on trying to program so bear with me. I am working on the problem set 1a of the intro to cs open course ware. I will attach the code I have so far at the bottom. It will calculate right to a certain number but won't once I go so far. My question is what am I doing wrong? Am I going about it the completely wrong way?

number=2
primecount=0
while primecount<500:
if (number!=2) and (number%2 == 0) or (number!=3) and (number%3 == 0) or (number!=5) and (number%5 == 0) or (number!=7) and (number%7 == 0) or (number!=11) and (number%11 == 0) or (number!=13) and (number%13 == 0

Answer 1

Ok, so the whole code did not show up so I am going to attach the file.

Answer 2

please use a code pasting site:

- http://dpaste.com
- http://pastebin.com
- https://gist.github.com/
- http://pastie.org
- http://codepad.org
- http://ideone.com
- http://www.repl.it/

paste your code there and post the link here. select Python syntax highlighting when u paste.

http://dpaste.com/1536542/

Answer 3

what is the definition of a prime number?

Answer 4

Sorry about the attachment. I will use a pasting site if I have any further questions. And it is a number that is only divisible by 1 and itself. How would I test for this though? As I am typing this I was googling prime numbers and saw something called AKS primality test. Could I use this to do the calculations instead of the mess I created?

Answer 5

The testing that you're doing is all literal values. You need to stop and think about how you could do this with a formula and/or a data structure.

Hint: there's a fact about factoring non-prime numbers that can make your program run faster.

Answer 6

I fixed the code so it now runs along the same line you started on. It seems to perform it's job but i only checked quickly.

If you have any questions about the changes or anything I am available.

Answer 7

You're doing it wrong.

Suppose you have a list of primes less than `n`.
How would you check that `n` is prime using that list?

Answer 8

As you find new primes, continue to add them to your prime list.

Answer 9

Consider the following:
```
primes = [] # list of primes
primecount = 500 # number of primes to find
number = 2 # starting point
while len(primes) < primecount:
# write something here to determine if number is prime
if number_is_prime:
# add number to the list of primes
# print out number
number += 1 #move onto the next number
```