CODEWITHSUNDEEP
pythonpython-2.7
Oxide
Oxide

Reputation: 45

Python Overflow error: int too large to convert to C long

I'm a beginner and I'm doing the problems in and while doing the third problem, which is about finding the largest prime factor of 600851475143, I get this error:

Python int too large to convert to C long

plist = [2]


def primes(min, max):
    if 2 >= min:
        yield 2
    for i in xrange(3, max, 2):
        for p in plist:
            if i % p == 0 or p * p > i:
                break
        if i % p:
            plist.append(i)
            if i >= min:
                yield i


def factors(number):
    for prime in primes(2, number):
        if number % prime == 0:
            number /= prime
            yield prime
        if number == 1:
            break

a = 600851475143
print max(factors(a))

Upvotes: 0

Views: 5801

Answers (2)

Casey Williams
Casey Williams

Reputation: 96

This occurs when the number you are dealing with is greater than sys.maxsize

You could possibly use the numpy module and use a larger data type. Not sure how large you need without checking though.

Upvotes: -1

user2357112
user2357112

Reputation: 280708

Annoyingly, in Python 2, xrange requires its arguments to fit into a C long. 600851475143 is too big for that on your system. You'll have to rewrite your algorithm to not need such a big range, or use a substitute, such as your own xrange implementation, or a while loop with manual counter management.

Upvotes: 2

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