tkinter moving an class object with keybinds

[deanhystad]

The main purpose of a class is to define a template for reusable code. Your ship class can never be used anywhere that doesn't have a canvas named c1, a main window named r, and worst of all, an instance of ship named s. It is rare that a class references an instance of itself unless it is a singleton, or maintains a list of instances for some reason (pool allocation for example). My inclination is to write the code like this:

from tkinter import *

class Ship():
    def __init__(self, parent, wide, high):
        self.canvas = Canvas(parent, width=wide, height=high)
        self.canvas.pack()
        self.img = PhotoImage(file = "test_image.png")
        img_wide = self.img.width()
        img_high = self.img.height()
        self.xmax = wide - img_wide
        self.ymax = high - img_high
        self.x = int((wide - img_wide) / 2)
        self.y = int((high - img_high) / 2)
        self.img_id = self.canvas.create_image(self.x, self.y, anchor=NW, image=self.img)

    def move(self, x, y):
        x = max(-self.x, min(x, self.xmax - self.x))
        y = max(-self.y, min(y, self.ymax - self.y))
        self.x += x
        self.y += y
        self.canvas.move(self.img_id, x, y)
 
root = Tk()
ship = Ship(root, 500, 400)
root.bind("<Right>", lambda event: ship.move(x=5, y=0))
root.bind("<Left>", lambda event: ship.move(x=-5, y=0))
root.bind("<Up>", lambda event: ship.move(x=0, y=-5))
root.bind("<Down>", lambda event: ship.move(x=0, y=5))
root.mainloop()

I also changed things so the ship starts out in the middle of the sea (canvas) and is prevented from sailing off the edge.