Python中变量的内存大小 [英] Variable's memory size in Python

问题描述

我正在编写Python代码来进行一些大数计算，并且非常担心计算中使用的内存.

I am writing Python code to do some big number calculation, and have serious concern about the memory used in the calculation.

因此，我想计算每个变量的每一位.

Thus, I want to count every bit of each variable.

例如，我有一个变量 x ，它是一个很大的数字，并且想要计算表示 x 的位数.

For example, I have a variable x, which is a big number, and want to count the number of bits for representing x.

以下代码显然是无用的:

The following code is obviously useless:

x=2**1000
len(x)

因此，我转向使用以下代码:

Thus, I turn to use the following code:

x=2**1000
len(repr(x))

变量 x 为(十进制)为:

1071508607186267320948425049069068108105614048117055336074437503883703510511249361224931983788156958581275946729175531468251871452856923140435984577574698574803934567774824230985421074605062362371141877954182153043044984983581941267398767559165543946077062914571696477686476867678965

10715086071862673209484250490600018105614048117055336074437503883703510511249361224931983788156958581275946729175531468251871452856923140435984577574698574803934567774824230985421074605062371141877954182153046474983581941267398767559165543946077062914571196477686542167660429831652624386837205668069376

但是上面的代码返回 303

上面的long long序列的长度为302，因此我认为 303 应该仅与字符串长度有关.

The above long long sequence is of length 302, and so I believe that 303 should be related to the string length only.

所以，这是我最初的问题:

So, here comes my original question:

我怎么知道变量 x 的内存大小?

How can I know the memory size of variable x?

还有一件事情；如果我定义的话，使用C/C ++语言

One more thing; in C/C++ language, if I define

int z=1;

这意味着为 z 分配了4个字节= 32位，并且这些位安排为00..001(31个0和一个1).

This means that there are 4 bytes= 32 bits allocated for z, and the bits are arranged as 00..001(31 0's and one 1).

在这里，我的变量 x 很大，我不知道它是否遵循相同的内存分配规则?

Here, my variable x is huge, I don't know whether it follows the same memory allocation rule?

推荐答案

使用 sys.getsizeof 获取对象的大小(以字节为单位).

Use sys.getsizeof to get the size of an object, in bytes.

>>> from sys import getsizeof
>>> a = 42
>>> getsizeof(a)
12
>>> a = 2**1000
>>> getsizeof(a)
146
>>>

请注意，对象的大小和布局纯粹是特定于实现的.例如，CPython可能使用与IronPython完全不同的内部数据结构.因此，对象的大小可能因实现而异.

Note that the size and layout of an object is purely implementation-specific. CPython, for example, may use totally different internal data structures than IronPython. So the size of an object may vary from implementation to implementation.

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