enemy.py

import pygame
import os
import sys
from random import *


# how to add subclass to a sprite group in pygame
class SmallEnemy(pygame.sprite.Sprite):
    speed = 2

    def __init__(self, bg_size):
        pygame.sprite.Sprite.__init__(self)

        self.image = pygame.image.load("resource/images/enemy1.png").convert_alpha()
        self.rect = self.image.get_rect()
        self.width, self.height = bg_size[0], bg_size[1]
        self.speed = 2
        self.rect.left, self.rect.top = randint(0, self.width), randint(-5 * self.height, 0)

    def move(self):
        if self.rect.top < self.height:
            self.rect.top += self.speed
        else:
            self.reset()

    def reset(self):
        self.rect.left, self.rect.top = randint(0, self.width), randint(-5 * self.height, 0)


class MidEnemy(pygame.sprite.Sprite):
    def __init__(self, bg_size):
        pygame.sprite.Sprite.__init__(self)

        self.image = pygame.image.load("resource/images/enemy2.png").convert_alpha()
        self.rect = self.image.get_rect()
        self.width, self.height = bg_size[0], bg_size[1]
        self.speed = 1
        self.rect.left, self.rect.top = randint(0, self.width), randint(-10 * self.height,
                                                                        -self.height)  # unless wait a screen before arrive

    def move(self):
        if self.rect.top < self.height:
            self.rect.top += self.speed
        else:
            self.reset()

    def reset(self):
        self.rect.left, self.rect.top = randint(0, self.width), randint(-5 * self.height, 0)


class BigEnemy(pygame.sprite.Sprite):
    def __init__(self, bg_size):
        pygame.sprite.Sprite.__init__(self)

        self.image1 = pygame.image.load("resource/images/enemy3_n1.png.png").convert_alpha()
        self.image2 = pygame.image.load("resource/images/enemy3_n2.png.png").convert_alpha()
        self.rect = self.image.get_rect()
        self.width, self.height = bg_size[0], bg_size[1]
        self.speed = 1
        self.rect.left, self.rect.top = randint(0, self.width), randint(-15 * self.height,
                                                                        -5 * self.height)  # unless wait lot of screens before arrive

    def move(self):
        if self.rect.top < self.height:
            self.rect.top += self.speed
        else:
            self.reset()

    def reset(self):
        self.rect.left, self.rect.top = randint(0, self.width), randint(-5 * self.height, 0)