How to run executable file from cmake in python

So I have created a executable from cmake file name "COSMO" which is running fine if I run it from Linux command terminal

$ cat COSMO 

I am getting desired output But if I want to open same file using python I use

$ python3 file.py

where python3 file contains code

import subprocess

def executable_shell():
    x=subprocess.run('cd build && cat COSMO', shell=True, capture_output=True)
    print(x)
executable_shell()

to make sure cd command is not interfering I make a python file inside build directory where my cmake file is created.

now in both cases I am getting random gibbrish like when i open the executable from notepad. whereas if i run this file directly the format is fine.

if i use .stdout.decode() it is saying codec can't decode byte 0xf8 in position 96: invalid start byte

i have used my subprocess command and it is working fine for commands like ls, cd etc. so how will run it in python