Pygame Button test

#!/usr/bin/env python3

#
# pygame (empty) template - by furas
#

# ---------------------------------------------------------------------

__author__  = 'Bartlomiej "furas" Burek'
__webpage__ = 'http://blog.furas.pl'

# ---------------------------------------------------------------------

import pygame

# === CONSTANS === (UPPER_CASE names)

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

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

SCREEN_WIDTH  = 600
SCREEN_HEIGHT = 400

# === CLASSES === (CamelCase names)

import pygame.font

class Button():

    def __init__(self, ai_settings, screen, msg):
        """Inicjalizacja atrybutów przycisku."""
        self.screen = screen
        self.screen_rect = screen.get_rect()

        #Zdefiniowanie wymiarów i właściwości przycisku.
        self.width, self.height = 200, 50
        self.button_color = (0, 255, 0)
        self.text_color = (100, 255, 100)
        self.font = pygame.font.SysFont(None, 48)

        #Utworzenie prostokąta przycisku i wyświetlenie go.
        self.rect = pygame.Rect(0, 0, self.width, self.height)
        self.rect.center = self.screen_rect.center
        self.prep_msg(msg)

    def prep_msg(self, msg):
        """Umieszczenie komunikatu w wygenerowanym obrazie i
        wyśrodkowanie tekstu na przycisku"""
        self.msg_image = self.font.render(msg, True, self.text_color,
        self.button_color)
        self.msg_image_rect = self.msg_image.get_rect()
        self.msg_image_rect.center = self.rect.center

    def draw_button(self):
        #Wyświtlenie pustego przycisku, a następnie komunikatu na nim.
        self.screen.fill(self.button_color, self.rect)
        self.screen.blit(self.msg_image, self.msg_image_rect)

# === FUNCTIONS === (lower_case names)

    # empty

# === MAIN === (lower_case names)

# --- (global) variables ---

# --- init ---

pygame.init()

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

# --- objects ---

b = Button(None, screen, "Hello")

# --- mainloop ---

clock = pygame.time.Clock()
is_running = True

while is_running:

    # --- events ---

    for event in pygame.event.get():

        # --- global events ---

        if event.type == pygame.QUIT:
            is_running = False
        elif event.type == pygame.KEYDOWN:
            if event.key == pygame.K_ESCAPE:
                is_running = False

        # --- objects events ---

            # empty

    # --- updates ---

        # empty

    # --- draws ---

    screen.fill(BLACK)

    b.draw_button()

    pygame.display.update()

    # --- FPS ---

    clock.tick(25)

# --- the end ---

pygame.quit()