python中的等效C联合? [英] Equivalent C union in python?

问题描述

假设我在 C 中有以下代码

Say I'm having a following code in C

union u_type
{
    uint32_t data;
    uint8_t  chunk[4];
} 32bitsdata;

32bitsdata.chunk[0] = some number;
32bitsdata.chunk[1] = some number;
32bitsdata.chunk[2] = some number;
32bitsdata.chunk[3] = some number;

printf("Data in 32 bits: %d\n", 32bitsdata.data);

我如何在 python 中做类似的事情?

How could I do similar thing in python?

我正在尝试读取一个二进制文件(逐字节)- 已经开始工作，并将每 3 个字节合并为一个 int.听说 struct 可以解决问题，但我不确定如何.

I'm trying to read a binary file (byte by byte) - already got it working, and combining every 3 bytes into one int. Heard struct would do the trick, but I'm not really sure how.

最好，

亨利

推荐答案

ctypes?

from ctypes import (
        Union, Array, 
        c_uint8, c_uint32, 
        cdll, CDLL
) 

class uint8_array(Array):
    _type_ = c_uint8
    _length_ = 4

class u_type(Union):
    _fields_ = ("data", c_uint32), ("chunk", uint8_array)

# load printf function from Dynamic Linked Libary libc.so.6 (I'm use linux)
libc = CDLL(cdll.LoadLibrary('libc.so.6')._name)
printf = libc.printf

if __name__ == "__main__":
    # initialize union
    _32bitsdata = u_type()
    # set values to chunk
    _32bitsdata.chunk[:] = (1, 2, 3, 4)
    # and print it
    printf(b"Data in 32 bits: %d\n", _32bitsdata.data)

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