How to detect collisions between two rectangular objects or images in pygame

I am making a game in which the player has to use a bowl to catch falling items. I have some images of items in a list and an image of a bowl that is used to catch the items. The items keep on falling and reset to the top of the screen if they reach the boundary (bottom edge). I got this logic done which allows the items to fall but I do not know how to detect when there is a collision between the bowl and item.

My code:

import math
import pygame
import random


pygame.init()

display_width = 800
display_height = 600

game_display = pygame.display.set_mode((display_width, display_height))
clock = pygame.time.Clock()
pygame.display.set_caption("Catch the Ball")

white = (255, 255, 255)
black = (0, 0, 0)
red = (255, 0, 0)
blue = (0, 255, 0)

player_img = pygame.image.load("Images/soup.png")
thing_imgs = [pygame.image.load('Images/muffin.png'), pygame.image.load('Images/dessert.png'),
              pygame.image.load('Images/cheese.png'), pygame.image.load('Images/fruit.png')]


def player(x, y):
    game_display.blit(player_img, (x, y))


def things(x, y, img):
    game_display.blit(img, (x, y))


def game_loop():
    running = True

    x = display_width * 0.45
    y = display_height * 0.8
    x_change = 0

    player_width = 64
    player_height = 64

    things_cor = [[random.randint(0, display_width), 32]]
    things_added = [random.choice(thing_imgs)]
    thing_height = 32
    thing_width = 32
    y_change = 5

    caught = 0

    while running:
        for event in pygame.event.get():
            if event.type == pygame.QUIT:
                running = False

            if event.type == pygame.KEYDOWN:
                if event.key == pygame.K_LEFT:
                    x_change = -5

                if event.key == pygame.K_RIGHT:
                    x_change = 5

            if event.type == pygame.KEYUP:
                if event.key == pygame.K_LEFT or event.key == pygame.K_RIGHT:
                    x_change = 0

        game_display.fill(white)

        player(x, y)
        x += x_change

        for i in range(len(things_cor)):
            thing_x, thing_y = things_cor[i]
            things(thing_x, thing_y, things_added[i])

        for i in range(len(things_cor)):
            things_cor[i][1] += y_change
            if things_cor[i][1] > display_height:
                things_cor[i][1] = random.randint(-2000, -1000)
                things_cor[i][0] = random.randint(0, display_width)
                things_added[i] = random.choice(thing_imgs)

                things_added.append(random.choice(thing_imgs))

                if len(things_added) < 6:
                    things_cor.append(
                        [random.randint(0, display_width), -10])

        if x < 0:
            x = 0
        elif x > display_width - player_width:
            x = display_width - player_width

        clock.tick(60)
        pygame.display.update()


game_loop()

Answers:

Thank you for visiting the Q&A section on Magenaut. Please note that all the answers may not help you solve the issue immediately. So please treat them as advisements. If you found the post helpful (or not), leave a comment & I’ll get back to you as soon as possible.

Method 1

Use pygame.Rect objects and colliderect() to detect the collision between the bounding rectangles of 2 objects or 2 images:

rect1 = pygame.Rect(x1, y1, w1, h1)
rect2 = pygame.Rect(x2, y2, w2, h2)
if rect1.colliderect(rect2):
    # [...]

If you have to images (pygame.Surface objects), the bounding rectangle of can be get by get_rect(), where the location of the Surface has to be set by an keyword argument, since the returned rectangle always starts at (0, 0):
(see Why is my collision test not working and why is the position of the rectangle of the image always wrong (0, 0)?)

def game_loop():
    # [...]

    while running:
        # [...]

        player_rect = player_img.get_rect(topleft = (x, y))
        for i in range(len(things_cor)):
            thing_rect = things_added[i].get_rect(topleft = things_cor[i])

            if player_rect.colliderect(thing_rect):
                print("hit")

        player(x, y)
        x += x_change

        for i in range(len(things_cor)):
            thing_x, thing_y = things_cor[i]
            things(thing_x, thing_y, things_added[i]) 

Use pygame.time.get_ticks() to delay the start of the game for a certain time. pygame.time.get_ticks() return the number of milliseconds since pygame.init() was called. For instance:

def game_loop():
    # [...]

    while running:
        passed_time = pygame.time.get_ticks() # passed time in milliseconds
        start_time = 100 * 1000 # start time in milliseconds (100 seconds)
        
        # [...]

        # move player    
        if passed_time >= start_time:
            x += x_change
            if x < 0:
                x = 0
            elif x > display_width - player_width:
                x = display_width - player_width
    
        # move things
        if passed_time >= start_time:
            for i in range(len(things_cor)):
                things_cor[i][1] += y_change
                if things_cor[i][1] > display_height:
                    things_cor[i][1] = random.randint(-2000, -1000)
                    things_cor[i][0] = random.randint(0, display_width)
                    things_added[i] = random.choice(thing_imgs)

                    things_added.append(random.choice(thing_imgs))

                    if len(things_added) < 6:
                        things_cor.append(
                            [random.randint(0, display_width), -10])

        # draw scene and update dispaly
        game_display.fill(white)
        player(x, y)
        for i in range(len(things_cor)):
            thing_x, thing_y = things_cor[i]
            things(thing_x, thing_y, things_added[i])
        pygame.display.update()
        clock.tick(60)

All methods was sourced from stackoverflow.com or stackexchange.com, is licensed under cc by-sa 2.5, cc by-sa 3.0 and cc by-sa 4.0