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I am working on a homework problem for my Python course that is supposed to display a car (got that) and then the car is supposed to simulate driving across the window until it reaches the end, and then restarting at the beginning. I have a race function that is supposed to be doing this but it's not doing anything. I'm having a hell of a time with classes and tkinter. I know that I need the value of x to be incremented each time it loops and updates so that the car looks like its moving, I'm just not sure how to implement that. Is my boolean not written correctly? I've tried changing things around a few different ways with the function but I can't seem to get it to do anything, so I must be missing something.

UPDATE: I have moved the race method into the class, and called it within the constructor. I put a print statement to get the value of x in the race method and its showing that x is being incremented correctly, but when I run the program my car disappears. So it's updating the value of x as it should, but its not displaying the graphic. Code updated below

Any suggestions are appreciated! 

# Import tkinter
from tkinter import *

# Set the height and Width of the window
width = 800
height = 800

# Create race car class with canvas as the argument
class RacingCar(Canvas):

    # Constructor
    def __init__(self, master, width, height):

        # Constructor
        Canvas.__init__(self, master, width = width, height = height)

        # Create x and y variables for starting position
        self.x = 10
        self.y = 40

        # Display the car
        self.display_car()
        self.race()


    # Function to display car
    def display_car(self):

        # Delete original car
        self.delete("car")

        # Create first wheel
        self.create_oval(self.x + 10, self.y - 10, self.x + 20,\
                        self.y, fill = "black", tags = "car")

        # Create the second wheel
        self.create_oval(self.x + 30, self.y - 10, self.x + 40,\
                        self.y, fill = "black", tags = "car")

        # Create the body
        self.create_rectangle(self.x, self.y - 20, self.x + 50,\
                        self.y - 10, fill = "green", tags = "car")

        # Create the roof
        self.create_polygon(self.x + 10, self.y - 20, self.x + 20,\
                            self.y - 30, self.x + 30, self.y - 30,\
                            self.x + 40, self.y - 20, fill = "green",\
                            tags = "car")
        def race():
            while True:
               if self.x < width:
                  self.x += 2
               else: 
                  self.x = 0

                  self.after(88)

                  self.update()



window = Tk()
window.title("Racing Car")

racecar = RacingCar(window, width = 240, height = 50 )
racecar.pack()


window.mainloop()
Joseph Smith
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  • Why is you `race` method not in the `RacingCar` class? Also, the fact that you reference the `racecar` variable before assigning it is disturbing and could be a problem. – Romain Reboulleau Sep 28 '19 at 21:08
  • The function `race` does not have access to the instance `racecar`. You can provide the racecar as an input argument to the function. Better would be to add the `race` method to the class. – rinkert Sep 28 '19 at 21:09
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    Read [While Loop Locks Application](https://stackoverflow.com/questions/28639228/python-while-loop-locks-application) – stovfl Sep 28 '19 at 21:15

1 Answers1

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This might not get it done (so I make this answer a community wiki), but I suggest you move the race method in the class:

class RaceCar(Canvas):
    # Your current code
    def race(self):
        while True:
            if self.x < width:
                self.x += 2
            else:
                self.x = 0
            self.after(88)
            self.update()
Romain Reboulleau
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