[Tkinter] how do I enter code into python

[matelot]

I am hoping to run a program that links an arduino to a mechanical device and the information I have is to use python to do it and provides the program that includes pyserial so I need pyserial.
I am just about to delete the python software and try to reinstall it.

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I have now reloaded python In fact I found a 64 bit version that I loaded and did a custom load. Ticked the PATH box and saved the files in c;\users\bob\python36.
If I put my test file in python36 and remove the references to pyserial it works fine.
I assumed that ticking the path box would mean that python would run from anywhere, it seems not, if I put my test file (without the pyserial part) in c;\users\bob and try to run it from there I get a box saying
the application was unable to start correctly(0xc000007b)
I was hoping this would help with the fact that the pyserial files are elsewhere.
I am slowly moving forward but still need to be able to run the file that contains

## Rubik (Hello, World)             @ kas 2017

from tkinter import *
import serial, time
from serial import SerialException
import atexit
import subprocess

root =Tk()
root.title('Hello, World')
root.geometry('300x300+200+200')          ## window size + position

root.mainloop()

Any help would be appreciated.