I was doing a small serial communication system using pyserial. when I done the script on a .py file, it not worked. but when I opened
the python console and writed line by line the same code of the .py file, it worked.

the .py file:
import serial
ser = serial.Serial('com5')
ser.write('L'.encode())
ser.close()

it not worked.

on the python console:
python>> import serial
python>> ser = serial.Serial('com5')
python>> ser.write('L'.encode())
python>> ser.close()

It worked.

PySerial 3.4