Python OverflowError：无法将“long”放入索引=大小的整数中
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Python OverflowError: cannot fit 'long' into an index=sized integer
提问by
I want to generate two really large prime numbers using an algorithm I found online and changed slightly.
我想使用我在网上找到并略有更改的算法生成两个非常大的素数。
I get this error on line 5:
我在第 5 行收到此错误：
Python OverflowError: cannot fit 'long' into an index=sized integer
My code:
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
How can I fix my error?
我该如何修复我的错误？
If you know a better way to generate large primes, that would be helpful also.
如果您知道生成大素数的更好方法，那也会很有帮助。
采纳答案by Justin Peel
The following code demonstrates the problem that you are running into:
以下代码演示了您遇到的问题：
import sys
x = [True]*(sys.maxint+1)
which yields an OverflowError. If you instead do:
产生一个OverflowError. 如果你这样做：
x = [True]*(sys.maxint)
then you should get a MemoryError.
那么你应该得到一个MemoryError.
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.
这是发生了什么。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。
回答by 9000
Line 5 trues to allocate a really long list full of Truevalues. Probably your lngis too large to fit that list in memory?
第 5 行为 true 以分配一个非常长的充满True值的列表。可能您lng的文件太大而无法在内存中容纳该列表？
I was not able to exactly reproduce your error; in the worst case I ended up with just a MemoryErrorinstead.
我无法完全重现您的错误；在最坏的情况下，我最终只有一个MemoryError。
Probably the algorithm is ok (though I can't bet), just try a smaller number.
可能算法没问题（虽然我不能打赌），只是尝试一个较小的数字。
