Python for循环：“列表索引超出范围”错误？

Question

I have a code, based on problem 3 from Project Euler: "The prime factors of 13195 are 5, 7, 13 and 29. What is the largest prime factor of the number 600851475143?"

I have a code below that I thought would work, but line 9 ( for k in range(2,res[j]): ) keeps returning the error: "IndexError: list index out of range". It doesn't seem like I'm modifying my list as I move through my for loop, so I'm not sure what's wrong.

def find_primes(num):
    res = []
    print(num)

    for i in range(2,num):
        if num%i==0:
            res.append(i)

    for j in res:
        for k in range(2,res[j]):
           if res[j]%k==0:
               res[j]=False
    list(filter((False).__ne__, res))

    m = max(res)
    return(m)

Does anyone know where I'm going wrong?

Thank you!

Answer 1

You probably meant to do:

for j in range(len(res)):
    for k in range(2,res[j]):

Using for j in res will iterate over res elements.