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POVariable's memory size in Python
 

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  1. POVariable's memory size in Python
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    <p>I am writing Python code to do some big number calculation, and have serious concern about the memory used in the calculation.</p> <p>Thus, I want to count every bit of each variable.</p> <p>For example, I have a variable <strong>x</strong>, which is a big number, and want to count the number of bits for representing <strong>x</strong>.</p> <p>The following code is obviously useless:</p> <pre><code>x=2**1000 len(x) </code></pre> <p>Thus, I turn to use the following code:</p> <pre><code>x=2**1000 len(repr(x)) </code></pre> <p>The variable <strong>x</strong> is (in decimal) is:</p> <blockquote> <p>10715086071862673209484250490600018105614048117055336074437503883703510511249361224931983788156958581275946729175531468251871452856923140435984577574698574803934567774824230985421074605062371141877954182153046474983581941267398767559165543946077062914571196477686542167660429831652624386837205668069376</p> </blockquote> <p>but the above code returns <strong>303</strong></p> <p>The above long long sequence is of length 302, and so I believe that <strong>303</strong> should be related to the string length only.</p> <p>So, here comes my original question:</p> <p>How can I know the memory size of variable <strong>x</strong>?</p> <p>One more thing; in C/C++ language, if I define</p> <pre><code>int z=1; </code></pre> <p>This means that there are 4 bytes= 32 bits allocated for <strong>z</strong>, and the bits are arranged as 00..001(31 0's and one 1).</p> <p>Here, my variable <strong>x</strong> is huge, I don't know whether it follows the same memory allocation rule? </p>
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    1. USuser4478
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    1. COI just found that sys.getsizeof(x) seems to be useful? I use sys.getsizeof(x), where x=2**1000 and such instruction returns 160. Does this means that x occupies 160 bytes? Or actually 160 bits?
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    2. COUnless you're dealing with extremely low-level hardware implementation, no one measures anything in bits. For most all intents and purposes the lowest unit of computing is the `byte`.
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      1. USJonathon Reinhart
 

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