如何在二进制级别上将 integer 解释为 python 中的不同类型

Question

I want to do the following:

a = 4
b = 7

result = int([a, b]) # Result is 1031 or 1796 depending on the endianness

So essentially lay out two unsigned integers next to each other, as one byte, and interpret the region as a two-byte unsigned integer.

Is this possible given python's generic int ?

Answer 1

You have to use bitwise operations: a << 8 | b a << 8 | b

Explanation:

First, a << 8 is evaluated. It's a left shift, so all the bits are going 8 places to the left:

0000 0000 0000 0100
          ↙↙↙ ↙↙↙
        ↙↙↙ ↙↙↙
      ↙↙↙ ↙↙↙
   ↙↙↙ ↙↙↙
↙↙↙ ↙↙↙
0000 0100 0000 0000

Then the | operator (bitwise or) is evaluated.

   0000 0100 0000 0000  #<= a<<8
OR 0000 0000 0000 0111  #<= b
----------------------
=  0000 0100 0000 0111  #<= a<<8 | b, decimal 1031
======================

The result of the bitwise OR ist an 1 wherever at least one operand has an 1 at this place. Here it's used to "merge" the two numbers together. Because the left byte of b is all 0 it doesn't affect the left byte of the first operand and vice versa.