Previous sprites staying when changing y_positions to move - pygame

Question

I'm making a game where the player controls a sprite that catches falling food.
However, I'm having trouble with the falling food part.
import pygame
import random
import time
d_w = 800
d_h = 600
fall_speed = 5
screen = pygame.display.set_mode((d_w, d_h))
clock = pygame.time.Clock()
BGCOLOR = (0, 155, 0)
goodFood = pygame.image.load('burg.png')
def randFoodGen():
x_food = d_w/2
y_food = 0
return x_food,y_food
def BurgGen():
x_food, y_food = randFoodGen()
screen.fill(BGCOLOR)
while True:
y_food = y_food + fall_speed
if y_food > d_w:
x_food = (random.randrange(0, d_w))
y_food = -30
screen.blit(goodFood, [x_food, y_food])
pygame.display.update()
clock.tick(30)
BurgGen()
It ends up keeping the previous position of the falling food sprite, like this:
Anger

Answer 1

Your screen.fill(BGCOLOR) needs to be within the while loop.
def BurgGen():
x_food, y_food = randFoodGen()
while True:
screen.fill(BGCOLOR)
y_food = y_food + fall_speed
if y_food > d_w:
x_food = (random.randrange(0, d_w))
y_food = -30
screen.blit(goodFood, [x_food, y_food])
pygame.display.update()
clock.tick(30)
That will at least solve the persisting burger problem. The reason is that before you draw a new burger, you have to wipe the screen of the burger you drew previously.
Also, if you are going to have multiple falling objects, you might want to make a pygame.Rect to represent each falling object. You might also want to make a python list of those pygame.Rect objects.
falling_objects = [] # create empty list
Whenever you need to create a new falling object, create a pygame.Rect and .append it to the list.
new_object = pygame.Rect(x, y, width, height)
falling_objects.append(new_object)
Then, to update the objects positions, you loop through the list and update the Rects
for obj_rect in falling_objects:
obj_rect.move_ip(0, fall_speed)
Use a similar for-loop to blit the image at each location
for obj_rect in falling_objects:
screen.blit(food_image, obj_rect.top_left)
A bit in-depth but I hope that helps a bit.