Run python in terminal and don't terminate when terminal is closed

Use the nohup shell builtin:

nohup python -m http.server 55550

To terminate the process, simply kill it using the kill command, just like any other process.

you can also launch it in background

python -m http.server 55550 &

then enter

disown

to detach the process to the current term

screen
python -m SimpleHTTPServer 55550 &
press ctrl+a, then press d
exit

shutdown your computer
...
start your computer
ssh your server
screen -r