When I call a executable in python using os.system("./mydemo") in Ubuntu, it can't find the .so file (libmsc.so) needed for mydemo. I used os.system("export LD_LIBRARY_PATH=pwd:$LD_LIBRARY_PATH;"), but it still can't find libmsc.so.
The libmsc.so is in the current directory. and shouldn't be global.
If I remember correctly, executing export ... via os.system will only set that shell variable within the scope, thus it's not available in the following os.system scopes. You should set the LD_LIBRARY_PATH in the shell, before executing the Python script.
Btw. also avoid setting relative paths…
I use os.system to run executable file, but it need a .so file, it can't find library