Python - Pygame - butterflies example

# pygame simple template - by furas

import pygame
import random

''' click butterfly to freeze/unfreeze it '''

# === CONSTANTS === UPPER_CASE names

SCREEN_WIDTH = 800
SCREEN_HEIGHT = 600

FPS = 10

BLACK = (  0,   0,   0)
WHITE = (255, 255, 255)

RED   = (255,   0,   0)
GREEN = (  0, 255,   0)
BLUE  = (  0,   0, 255)

CYAN  = (  0, 255, 255)

# === CLASSES === CamelCase names

class Butterfly:

    def __init__(self):

        img1 = pygame.Surface( (50,50) )
        img1.fill(RED)

        img2 = pygame.Surface( (50,50) )
        img2.fill(GREEN)

        img3 = pygame.Surface( (50,50) )
        img3.fill(BLUE)

        # animation frames
        self.images = [
            #pygame.image.load('butterflya.png'),
            #pygame.image.load('butterflyb.png'),
            img1,
            img2,
            img3,
        ]

        # numbers of frames
        self.images_count = len(self.images)

        # start at random frame
        self.current_image = random.randint(0, self.images_count-1)

        # image of freezed butterfly
        self.image_of_freezed_butterfly = pygame.Surface( (50,50) )
        self.image_of_freezed_butterfly.fill(BLACK)

        # current image to draw
        self.image = self.images[self.current_image]

        # currrent positon
        self.rect = self.images[0].get_rect()
        self.set_random_position()

        # start as unfreezed
        self.freezed = False


    def set_random_position(self):
        self.rect.x = random.randint(0, SCREEN_WIDTH-self.rect.width)
        self.rect.y = random.randint(0, SCREEN_HEIGHT-self.rect.height)


    def update(self, surface_rect):
        if not self.freezed:
            self.rect.x += random.randint(-10,10)
            self.rect.y += random.randint(-10,10)
            self.rect.clamp_ip(surface_rect)

            self.current_image = (self.current_image + 1) % self.images_count
            self.image = self.images[self.current_image]
        else:
            self.image = self.image_of_freezed_butterfly


    def draw(self, surface):
        surface.blit(self.image, self.rect)


    def event_handle(self, event):

        if event.type == pygame.MOUSEBUTTONDOWN:
            if event.button == 1: # left button
                if self.rect.collidepoint(event.pos):
                    print("butterfly clicked at", event.pos)

                    # feeze/unfreez on click
                    self.freezed = not self.freezed


# === FUNCTIONS === lower_case names

# empty

# === MAIN ===

# --- init ---

pygame.init()

screen = pygame.display.set_mode((SCREEN_WIDTH, SCREEN_HEIGHT))
screen_rect = screen.get_rect()

pygame.display.set_caption('Butterflies')

# --- objects ---

net = []

for _ in range (15):
    net.append( Butterfly() )

# --- mainloop

clock = pygame.time.Clock()

running = True

while running:

    # --- events ---

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

        if event.type == pygame.KEYDOWN:
            if event.key == pygame.K_ESCAPE:
                running = False

        # --- objects event ---

        for butterfly in net:
            butterfly.event_handle(event)

    # --- updates (without draws) ---

    for butterfly in net:
        butterfly.update(screen_rect)

    # --- draws (without updates) ---

    screen.fill(CYAN)

    for butterfly in net:
        butterfly.draw(screen)

    pygame.display.update()

    clock.tick(FPS)

# --- the end ---

pygame.quit()