Our example will consist of a simple canvas with a rectangle item, which can be moved horizontally and vertically using the arrow keys.

To prevent this item from moving outside of the screen, we will limit its movements inside the canvas dimensions:

import tkinter as tk

class App(tk.Tk):
    def __init__(self):
        super().__init__()
        self.title("Moving canvas items")

        self.canvas = tk.Canvas(self, bg="white")
        self.canvas.pack()
        self.update()
        self.width = self.canvas.winfo_width()
        self.height = self.canvas.winfo_height()

        self.item = self.canvas.create_rectangle(30, 30, 60, 60,
                                                 fill="blue")
        self.pressed_keys = {}
        self.bind("<KeyPress>", self.key_press)
        self.bind("<KeyRelease>", self.key_release)
        self.process_movements()

    def key_press(self, event):
        self.pressed_keys[event.keysym] = True

    def key_release(self, event):
        self.pressed_keys.pop(event.keysym, None)

    def process_movements(self):
        off_x, off_y = 0, 0
        speed = 3
        if 'Right' in self.pressed_keys:
            off_x += speed
        if 'Left' in self.pressed_keys:
            off_x -= speed
        if 'Down' in self.pressed_keys:
            off_y += speed
        if 'Up' in self.pressed_keys:
            off_y -= speed

        x0, y0, x1, y1 = self.canvas.coords(self.item)
        pos_x = x0 + (x1 - x0) / 2 + off_x
        pos_y = y0 + (y1 - y0) / 2 + off_y
        if 0 <= pos_x <= self.width and 0 <= pos_y <= self.height:
            self.canvas.move(self.item, off_x, off_y)

        self.after(10, self.process_movements)

if __name__ == "__main__":
    app = App()
    app.mainloop()