How to program Arduino LCD shield with Python?
It's like @chrisl wrote in the comments. You cannot program Arduino with python.

You can however upload an open source Firmata protocol implementation onto the Arduino and then write python code on your PC that will send commands to the Arduino by USB cable to tell it what to do.

This way you actually execute your code on PC, but control Arduino pins. Only drawback is that you need to have a PC connected to the Arduino at all times. This is not very practical.

There is a really nice tutorial here

Example python code looks like this:

import pyfirmata
import time

board = pyfirmata.Arduino('/dev/ttyACM0')
while True:
    board.digital[13].write(1)
    time.sleep(1)
    board.digital[13].write(0)
    time.sleep(1)


I'm afraid that only solution to controlling LCD shield this way without writing any C is to write the entire LCD library in python basing on pyfirmata calls to control the Arduino pins. It's not as hard as it sounds, and even a beginner could easily succeed.