Repeating Code in Python for Colour Changing Program

Question

I was writing a feature for a game where the user can press a key on the keyboard and that would change the colour of all the objects drawn on the screen to that colour. For example, if g is pressed, everything turns green.

To do this, I could write:

while True:
    while start==True:
        clock.tick(30)
        for event in pygame.event.get():
            if event.type == QUIT:
                pygame.quit()
                sys.exit()
            if event.type == pygame.KEYDOWN:
                if event.key == K_SPACE:
                    start =False
                    match_start=time.time()
                if event.key==K_w:
                    colour=white
                elif event.key==K_g:
                    colour=green
                elif event.key==K_y:
                    colour=yellow
                elif event.key==K_b:
                    colour=blue
                elif event.key==K_r:
                    colour=red
                elif event.key==K_p:
                    colour=purple

This code works perfectly well. However, I need to write the exact same code later on. To avoid repetition, I considered encapsulating the code using a function like this:

def set_colour():
    if event.key==K_w:
        colour=white
    elif event.key==K_g:
        colour=green
    elif event.key==K_y:
        colour=yellow
    elif event.key==K_b:
        colour=blue
    elif event.key==K_r:
        colour=red
    elif event.key==K_p:
        colour=purple

Then later in the program I could call the function on multiple occassions at several different points in the code, like this:

while True:
    while start==True:
        clock.tick(30)
        for event in pygame.event.get():
            if event.type ==QUIT:
                pygame.quit()
                sys.exit()
            if event.type == pygame.KEYDOWN:
                if event.key ==K_SPACE:
                    start =False
                    match_start=time.time()
                set_colour()

Unfortunately, this does not work. I have not received an error message, but the colour does not change when one of the defined keys is pressed. I think this is something to do with the function requiring more input data, but I'm not sure.

I would appreciate any advice you can give.

Answer 1

It doesn't seem like you've passed the event to your set_colour() function for it to use and then your function doesn't return back the chosen color or do anything with it for the colour to change. It seems like your function is only changing the local colour variable instead of the one in the scope for where the function is called.

You probably want to change the function to return the chosen colour and have the event be passed in as a parameter like this:

def set_colour(event):
    colour = None  # Make sure colour is initialized
    if event.key == K_w:
        colour = white
    elif event.key == K_g:
        colour = green
    elif event.key == K_y:
        colour = yellow
    elif event.key == K_b:
        colour = blue
    elif event.key == K_r:
        colour = red
    elif event.key == K_p:
        colour = purple

    return colour

Then in your code where you call this function do it like so:

colour = set_colour(event)