How can I apply a limit on input(not more than 20 letters) and the input value can be just alphabet?

Question

def save_load_page():
    bg = pygame.image.load(resource_path("./Game_Assets/Backgrounds/menu_background.png"))
    bg = pygame.transform.scale(bg,(900,600))  
    ogre_set = pygame.image.load(resource_path("./Game_Assets/Character_Name/Ogre_Character_Overview.png"))
    ogre_set = pygame.transform.scale(ogre_set,(844,420))

    name_input = ''
    change_click = False
    click = False
    while True:
        mx, my = pygame.mouse.get_pos()
        screen.blit(bg,(0,0))
        screen.blit(ogre_set,(22,140))
        text_surface = base_font.render(name_input,True,(255,255,255))
        screen.blit(text_surface,(60, 445))
        # Logic goes here

        change_click = False
        click = False
        # Event Collections
        for event in pygame.event.get():
            # Function to quit game
            '''if event.type == QUIT:
                event.quit()
                sys.exit()'''
            if event.type == KEYDOWN:
                if event.key == K_RETURN:
                    pass
                elif event.key == K_KP_ENTER:    
                    ogre1_name = name_input
                    break
                elif event.unicode == K_alpha:
                    name_input += event.Ascii
                    if len(name_input) <= 21:
                        pass  
                while name == '' or len(name) > 20 or name in names_list:                         
            if event.type == MOUSEBUTTONDOWN:
                if event.button == 1:
                    change_click = True
            if event.type == MOUSEBUTTONDOWN:
                if event.button == 1:
                    click = True

        pygame.display.update()
        clock.tick(120)

Answer 1

You have to evaluate if the length of the text is less than 20, before you add the new character. isalpha() can be used to test whether a character is a letter (see How can I check if character in a string is a letter?):

if event.type == KEYDOWN:
    if event.key == K_RETURN:
        # [...]
    elif event.key == K_KP_ENTER:    
        # [...]
                        
    elif len(name_input) < 20 and event.unicode.isalpha():
        name_input += event.unicode