Python OverflowError:无法将“long"放入索引=大小的整数中 [英] Python OverflowError: cannot fit 'long' into an index=sized integer

问题描述

我想使用我在网上找到并稍有改动的算法生成两个非常大的素数.

I want to generate two really large prime numbers using an algorithm I found online and changed slightly.

我在第 5 行收到此错误:

I get this error on line 5:

Python OverflowError: cannot fit 'long' into an index=sized integer 

我的代码:

import math
def atkin(end):  
    if end < 2: return []  
    lng = ((end/2)-1+end%2)   
    **sieve = [True]*(lng+1)**  
    for i in range(int(math.sqrt(end)) >> 1):
        if not sieve[i]: continue  
        for j in range( (i*(i + 3) << 1) + 3, lng, (i << 1) + 3):  
            sieve[j] = False  
    primes = [2]  
    primes.extend([(i << 1) + 3 for i in range(lng) if sieve[i]])  
    return primes

我该如何修复我的错误?

How can I fix my error?

如果您知道生成大素数的更好方法，那也会很有帮助.

If you know a better way to generate large primes, that would be helpful also.

推荐答案

以下代码演示了您遇到的问题:

The following code demonstrates the problem that you are running into:

import sys
x = [True]*(sys.maxint+1)

产生一个 OverflowError.如果您改为这样做:

which yields an OverflowError. If you instead do:

x = [True]*(sys.maxint)

那么你应该得到一个MemoryError.

这是怎么回事.Python 可以使用自己的可扩展数据类型处理任意大的整数.但是，当您尝试创建像上面这样的列表时，Python 会尝试将小列表的重复次数(Python 整数)转换为 Py_ssize_t 类型的 C 整数.Py_ssize_t 的定义因构建而异，但可以是 ssize_t、long 或 int.本质上，Python 在进行转换之前会检查 Python 整数是否适合 C 整数类型，如果它不起作用，则会引发 OverflowError.

Here is what is going on. Python can handle arbitrarily large integers with its own extendible data type. However, when you try to make a list like above, Python tries to convert the number of times the small list is repeated, which is a Python integer, to a C integer of type Py_ssize_t. Py_ssize_t is defined differently depending on your build but can be a ssize_t, long, or int. Essentially, Python checks if the Python integer can fit in the C integer type before doing the conversion and raises the OverflowError if it won't work.

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