Exemplo mínimo de desenhar linhas com o mouse no Tkinter (vide mais referências de Tkinter abaixo)

tkinter_lines.py

# Baseado em https://stackoverflow.com/a/40877887/19771

from tkinter import *

current = None

def DrawGrid(drawing_area, line_distance):

   for x in range(line_distance,600,line_distance):
       drawing_area.create_line(x, 0, x, 600, fill="#d3d3d3")

   for y in range(line_distance,600,line_distance):
       drawing_area.create_line(0, y, 600, y, fill="#d3d3d3")

def main():
    root = Tk()
    drawing_area = Canvas(root, width=600, height=600, bg='white')
    drawing_area.pack()
    DrawGrid(drawing_area, 10)
    drawing_area.bind("<ButtonPress-3>", reset)  # botão da direita
    drawing_area.bind("<Motion>", motion)
    drawing_area.bind("<ButtonPress-1>", Mousedown)  # botão da esquerda

    root.mainloop()

def reset(event):
    global current
    current = None

def Mousedown(event):
    global current

    event.widget.focus_set()  # so escape key will work

    if current is None:
        # the new line starts where the user clicked
        x0 = event.x
        y0 = event.y

    else:
        # the new line starts at the end of the previously
        # drawn line
        coords = event.widget.coords(current)
        x0 = coords[2]
        y0 = coords[3]

    # create the new line
    current = event.widget.create_line(x0, y0, event.x, event.y)

def motion(event):
    if current:
        # modify the current line by changing the end coordinates
        # to be the current mouse position
        coords = event.widget.coords(current)
        coords[2] = event.x
        coords[3] = event.y

        event.widget.coords(current, *coords)

main()

z.md

Eventos acionados por teclas e outros "bindings":

• https://python-course.eu/tkinter_events_binds.php

Janelas de mensagem e painel de abrir arquivos ("dialogs"):

• https://python-course.eu/tkinter_dialogs.php

import tkinter as tk
from tkinter.colorchooser import askcolor                  
from tkinter import filedialog as fd 

def picker_callback():
    result = askcolor(
        color="#6A9662", 
        title="Color Picker"
    ) 
    print(result)

def open_callback():
    name= fd.askopenfilename(title="Escolha um arquivo")
    print(name)

def quit_procedure():
    print('Tratar encerramento aqui')
    root.destroy() # sem isto agora não fecha a janela!

root = tk.Tk()

root.wm_protocol ("WM_DELETE_WINDOW", quit_procedure) # captura o fechamento com X da janela

tk.Button(
    root, 
    text='Choose Color', 
    fg="darkgreen", 
    command=picker_callback
).pack(side=tk.LEFT, padx=10)

tk.Button(
    text='File Open', 
    command=open_callback
).pack(fill=tk.X)

tk.Button(
    text='Quit', 
    command=quit_procedure,  # no exemplo original era command=root.quit,
    fg="red"
).pack(side=tk.LEFT, padx=10)

tk.mainloop()

# about quit/destroy:
# https://bytes.com/topic/python/answers/390009-quitting-tkinter-application-confirmation
# -> https://stackoverflow.com/questions/4643007/intercept-tkinter-exit-command