Simple snake game in Python

Question

I have created a snake game in Python. It is a single-player game, where the snake has to eat the red dots in order to grow longer. I just wanted to review if there are any improvements.

import turtle
import random
import time
screen = turtle.Screen()
screen.title('Snake made in Python')
screen.setup(width = 800, height = 700)
screen.tracer(0)
turtle.bgcolor('turquoise')
turtle.speed(5)
turtle.pensize(4)
turtle.penup()
turtle.goto(-310,250)
turtle.pendown()
turtle.color('black')
turtle.forward(600)
turtle.right(90)
turtle.forward(500)
turtle.right(90)
turtle.forward(600)
turtle.right(90)
turtle.forward(500)
turtle.penup()
turtle.hideturtle()
score = 0
delay = 0.1
snake = turtle.Turtle()
snake.speed(0)
snake.shape('square')
snake.color("black")
snake.penup()
snake.goto(0,0)
snake.direction = 'stop'
fruit = turtle.Turtle()
fruit.speed(0)
fruit.shape('circle')
fruit.color('red')
fruit.penup()
fruit.goto(30,30)
old_fruit=[]
scoring = turtle.Turtle()
scoring.speed(0)
scoring.color("black")
scoring.penup()
scoring.hideturtle()
scoring.goto(0,300)
scoring.write("Score :",align="center",font=("Courier",24,"bold"))
def snake_go_up():
 if snake.direction != "down":
 snake.direction = "up"
def snake_go_down():
 if snake.direction != "up":
 snake.direction = "down"
def snake_go_left():
 if snake.direction != "right":
 snake.direction = "left"
def snake_go_right():
 if snake.direction != "left":
 snake.direction = "right"
def snake_move():
 if snake.direction == "up":
 y = snake.ycor()
 snake.sety(y + 20)
 if snake.direction == "down":
 y = snake.ycor()
 snake.sety(y - 20)
 if snake.direction == "left":
 x = snake.xcor()
 snake.setx(x - 20)
 if snake.direction == "right":
 x = snake.xcor()
 snake.setx(x + 20)
screen.listen()
screen.onkeypress(snake_go_up, "Up")
screen.onkeypress(snake_go_down, "Down")
screen.onkeypress(snake_go_left, "Left")
screen.onkeypress(snake_go_right, "Right")
while True:
 screen.update()
 if snake.distance(fruit)< 20:
 x = random.randint(-290,270)
 y = random.randint(-240,240)
 fruit.goto(x,y)
 scoring.clear()
 score+=1
 scoring.write("Score:{}".format(score),align="center",font=("Courier",24,"bold"))
 delay-=0.001
 
 new_fruit = turtle.Turtle()
 new_fruit.speed(0)
 new_fruit.shape('square')
 new_fruit.color('red')
 new_fruit.penup()
 old_fruit.append(new_fruit)
 
 
 for index in range(len(old_fruit)-1,0,-1):
 a = old_fruit[index-1].xcor()
 b = old_fruit[index-1].ycor()
 old_fruit[index].goto(a,b)
 
 if len(old_fruit)>0:
 a= snake.xcor()
 b = snake.ycor()
 old_fruit[0].goto(a,b)
 snake_move()
 if snake.xcor()>280 or snake.xcor()< -300 or snake.ycor()>240 or snake.ycor()<-240:
 time.sleep(1)
 screen.clear()
 screen.bgcolor('turquoise')
 scoring.goto(0,0)
 scoring.write(" GAME OVER \n Your Score is {}".format(score),align="center",font=("Courier",30,"bold"))
 
 for food in old_fruit:
 if food.distance(snake) < 20:
 time.sleep(1)
 screen.clear()
 screen.bgcolor('turquoise')
 scoring.goto(0,0)
 scoring.write(" GAME OVER \n Your Score is {}".format(score),align="center",font=("Courier",30,"bold"))
 
 time.sleep(delay)
turtle.Terminator()

Answer 1

UX

It is not obvious what the user should do when the GUI opens up. You should display some simple instructions in the GUI, such as:

Use arrow keys on keyboard to move right, left, etc.

When I exit out of the GUI window, I see several errors in the shell in which I ran the game. Perhaps this is specific to the version of Python I am using.

Efficiency

In the snake_move function, the 4 if statements should be combined into a single if/elif because the 4 conditions are mutually exclusive:

def snake_move():
 if snake.direction == "up":
 y = snake.ycor()
 snake.sety(y + 20)
 elif snake.direction == "down":
 y = snake.ycor()
 snake.sety(y - 20)
 elif snake.direction == "left":
 x = snake.xcor()
 snake.setx(x - 20)
 elif snake.direction == "right":
 x = snake.xcor()
 snake.setx(x + 20)

You should also be able to eliminate the intermediate variables. For example:

 if snake.direction == "up":
 snake.sety(snake.ycor() + 20)

Magic number

The 20 in the snake_move function should be a declared constant. You should also add a comment describing why you chose this value.

DRY

The 4 functions:

def snake_go_up():
def snake_go_down():
etc.

could be combined into a single function with an argument passed in corresponding to the direction.

This group of lines is repeated twice:

time.sleep(1)
screen.clear()
screen.bgcolor('turquoise')
scoring.goto(0,0)
scoring.write(" GAME OVER \n Your Score is {}".format(score),align="center",font=("Courier",30,"bold"))

They can be placed into a function.

Layout

Move the functions to the top after the import lines. Having them in the middle of the code interrupts the natural flow of the code (from a human readability standpoint).

There is inconsistent whitespace around operators, such as

 a= snake.xcor()
 b = snake.ycor()

The black program can be used to automatically format the code to add consistency. This will also help with the inconsistent indentation and excessive blank lines.