User-define function not working in Python

Question

#imports
import turtle
import time

delay = 0.1

#design
window = turtle.Screen()
window.title("Snake Game by LZ")
window.bgcolor("#cce0ff")
window.setup(width=700, height=750)
window.tracer(0)

head = turtle.Turtle()
head.speed(0)
head.shape("circle")
head.color("black")
head.penup()
head.goto(0,0)
head.direction = "stop"

#functions
def go_up():
    head.direction = "up"
    
def go_down():
    head.direction = "down"
    
def go_left():
    head.direction = "left"
    
def go_right():
    head.direction = "right"
    
def motion():
    if head.direction == "up":
        y = head.ycor()
        head.sety(y + 10)

def motion():
    if head.direction == "down":
        y = head.ycor()
        head.sety(y - 10)
        
def motion():
    if head.direction == "left":
        x = head.xcor()
        head.setx(x - 10)
        
def motion():
    if head.direction == "right":
        x = head.xcor()
        head.setx(x + 10)

#keyboard bindings
window.listen()
window.onkeypress(go_up, "Up")
window.onkeypress(go_down, "Down")
window.onkeypress(go_left, "Left")
window.onkeypress(go_right, "Right")

#main game loop
while True:
    window.update()

    motion()

    time.sleep(delay)

window.mainloop()

Here's my problem: I created a very simple Python program where if you press the → key, a black circle will move towards the right and if you press ↑ key, it will move upwards. Somehow, only the → is responding/functioning while the other three keys aren't.

My user-define functions (go_up, go_down, go_left, go_right) all seem alright, but I just don't understand why only go_right is working while the others aren't. Could anyone help me?

Exactly, the namespace gets rewritten each time so only the last one actually holds that reference. — BeanBagTheCat
– BeanBagTheCat, Commented Jan 22, 2021 at 13:36

BeanBagTheCat · Accepted Answer · 2021-01-22 13:39:46Z

1

You redefine the motion() function every time you declare it. So when referring to it you only actually refer to the last one.

Try adding your conditions to 1 function as an if/else block

def motion():

    if head.direction == "up":
        y = head.ycor()
        head.sety(y + 10)

    elif head.direction == "down":
        y = head.ycor()
        head.sety(y - 10)
        
    elif head.direction == "left":
        x = head.xcor()
        head.setx(x - 10)
        
    elif head.direction == "right":
        x = head.xcor()
        head.setx(x + 10)

answered Jan 22, 2021 at 13:39

BeanBagTheCat

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