Question

I’ve written some C code that I would like to port to python, as I feel python is a better ‘concept’ language.

In my C code, I use memory reinterpretation to achieve my goals, for example:

sizeof(int)  is 4 byte sizeof(char) is 1 byte  char c[4]={0x01,0x30,0x00,0x80}; int* i=(int*)c;  *i has the value 0x80003001 

similarly if i have:

int* j = (int*)malloc(sizeof(int)); char* c = (char*)j; *j = 0x78FF00AA;  c is now {0xAA, 0x00, 0xFF, 0x78} 

I would like to do a similar thing in python, I realise that I can use bit operations to accomplish this:

chararray=[] num=1234567890 size=8  while len(chararray) < size:    char = chr( (num & 255 ) )    num = num >> 8    chararray.append(char) 

However I was hoping there would be a faster way of accomplishing this.

Does python have anything similar to C’s union?

Answer 1

You can use the struct module:

import struct  # Pack a Python long as if it was a C unsigned integer, little endian bytes = struct.pack('<I', 0x78FF00AA) print [hex(ord(byte)) for byte in bytes]  ['0xaa', '0x0', '0xff', '0x78'] 

Read the documentation page to find about datatypes, and pay attention to endianness.