start should already be the right direction. However,
/b attaches it to the same console. Now the problem is that when a console window is closed, any process associated with this console will also be closed.
You can either use
/b, then it will run in a new console. If you want to run it in the background without a console window though, then you would need to use a VBScript or third-party tool: Run a batch file in a completely hidden way
However, in that case you wouldn't see the stdout/stderr output anymore. You could redirect it to a file though, by wrapping it in a
cmd /c your_command > stdout.txt 2> stderr.txt call and starting this one through one of the aforementioned methods (VBScript, third-party tool, ...).
Alternatively, you could also hide your own console window before you exit. I just wrote a little one-line program which does exactly that (source code is basically
ShowWindow(GetConsoleWindow(), SW_HIDE)): http://share.cherrytree.at/showfile-24286/hide_current_console.exe
This way, you can use
start /b, and when you want to "close" your console (technically hide it), you would run
hide_current_console & exit which would hide the console and then close the cmd.exe process (not the python process) - in one line, since you can't type
exit after the console was already hidden.