Python Tkinter arrow Key game - Character movement example

Python Tkinter Events and Event Handling: Exercise-12 with Solution

Write a Python program to create a simple game using Tkinter where a character moves on arrow key presses. Implement event handling for left, right, up, and down arrow keys.

Sample Solution:

Python Code:

import tkinter as tk

# Constants for character size and movement step
CHARACTER_SIZE = 20
MOVEMENT_STEP = 10

class CharacterGame:
    def __init__(self, root):
        self.root = root
        self.root.title("Character Game")

        self.canvas = tk.Canvas(root, width=400, height=400, bg="white")
        self.canvas.pack()

        # Create the character as a rectangle
        self.character = self.canvas.create_rectangle(
            190, 190, 210, 210, fill="blue"
        )

        # Bind arrow key events to movement functions
        self.canvas.bind("<Left>", self.move_left)
        self.canvas.bind("<Right>", self.move_right)
        self.canvas.bind("<Up>", self.move_up)
        self.canvas.bind("<Down>", self.move_down)

        # Add focus to the canvas so that it can receive keyboard events
        self.canvas.focus_set()

    def move_left(self, event):
        self.canvas.move(self.character, -MOVEMENT_STEP, 0)

    def move_right(self, event):
        self.canvas.move(self.character, MOVEMENT_STEP, 0)

    def move_up(self, event):
        self.canvas.move(self.character, 0, -MOVEMENT_STEP)

    def move_down(self, event):
        self.canvas.move(self.character, 0, MOVEMENT_STEP)

if __name__ == "__main__":
    root = tk.Tk()
    game = CharacterGame(root)
    root.mainloop()

Explanation:

In the exercise above -

• Import the "tkinter" library.
• Define constants:
• CHARACTER_SIZE = 20: This constant defines the size of the character (rectangle) in pixels.
• MOVEMENT_STEP = 10: This constant defines the step size for each movement when an arrow key is pressed.
• Create a class "CharacterGame" which encapsulates the entire game.
• Initialize the game:
• In the init method, the game initializes by creating the main window, setting its title, and creating a canvas widget for drawing the character.
• self.root stores the main Tkinter window.
• self.canvas is a canvas widget created within the main window where the character will be displayed.
• self.character represents the character (a blue rectangle) drawn on the canvas.
• Bind arrow key events to movement functions:
• self.canvas.bind("<Left>", self.move_left): Binds the left arrow key event to the move_left method.
• self.canvas.bind("<Right>", self.move_right): Binds the right arrow key event to the move_right method.
• self.canvas.bind("<Up>", self.move_up): Binds the up arrow key event to the move_up method.
• self.canvas.bind("<Down>", self.move_down): Binds the down arrow key event to the move_down method.
• Add focus to the canvas:
• self.canvas.focus_set(): This line ensures that the canvas receives keyboard focus, allowing it to respond to arrow key presses.
• Define movement methods:
• move_left, move_right, move_up, and move_down are methods that move the character within the canvas based on the arrow key pressed. They use the self.canvas.move method to change the character's position.
• Create an instance of the CharacterGame class:
• root = tk.Tk(): Creates the main Tkinter window.
• game = CharacterGame(root): Creates an instance of the CharacterGame class, which initializes the game.
• root.mainloop(): Starts the Tkinter main event loop, allowing the game to run and respond to user input.
• Finally, start the Tkinter main loop with "root.mainloop()".

Output:

Flowchart:

Python Code Editor:

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