Pygame : Working with keyboard events

In this post, I am going to explain how to use key board UP, DOWN, LEFT and RIGHT arrow buttons to move a soldier to up, down left and right.

Step 1: First we should get notification, whenever key is pressed down and released. Event queue gets pygame.KEYDOWN, pygame.KEYUP events whenever key is pressed and released.

for event in pygame.event.get():
 if event.type == pygame.QUIT:
     dead = True

 if event.type == pygame.KEYDOWN:
    # Write logic

    if event.type == pygame.KEYUP:
    # Write logic

Step 2: We need to identify whether user pressed Left Arrow, Right Arrow, Down Arrow, UP Arrow. pygame.K_LEFT, pygame.K_RIGHT, pygame.K_UP, and pygame.K_DOWN constants are used to represent these keyboard buttons.

Following are the constants used to represent keys in the keyboard.

constant	ASCII	Key name
K_BACKSPACE	\b	backspace
K_TAB	\t	tab
K_CLEAR		clear
K_RETURN	\r	return
K_PAUSE		pause
K_ESCAPE	^[	escape
K_SPACE		space
K_EXCLAIM	!	exclaim
K_QUOTEDBL	"	quotedbl
K_HASH	#	hash
K_DOLLAR	$	dollar
K_AMPERSAND	&	ampersand
K_QUOTE		quote
K_LEFTPAREN	(	left parenthesis
K_RIGHTPAREN	)	right parenthesis
K_ASTERISK	*	asterisk
K_PLUS	+	plus sign
K_COMMA	,	comma
K_MINUS	-	minus sign
K_PERIOD	.	period
K_SLASH	/	forward slash
K_0	0	0
K_1	1	1
K_2	2	2
K_3	3	3
K_4	4	4
K_5	5	5
K_6	6	6
K_7	7	7
K_8	8	8
K_9	9	9
K_COLON	:	colon
K_SEMICOLON	;	semicolon
K_LESS	<	less-than sign
K_EQUALS	=	equals sign
K_GREATER	>	greater-than sign
K_QUESTION	?	question mark
K_AT	@	at
K_LEFTBRACKET	[	left bracket
K_BACKSLASH	\	backslash
K_RIGHTBRACKET	]	right bracket
K_CARET	^	caret
K_UNDERSCORE	_	underscore
K_BACKQUOTE	`	grave
K_a	a	a
K_b	b	b
K_c	c	c
K_d	d	d
K_e	e	e
K_f	f	f
K_g	g	g
K_h	h	h
K_i	i	i
K_j	j	j
K_k	k	k
K_l	l	l
K_m	m	m
K_n	n	n
K_o	o	o
K_p	p	p
K_q	q	q
K_r	r	r
K_s	s	s
K_t	t	t
K_u	u	u
K_v	v	v
K_w	w	w
K_x	x	x
K_y	y	y
K_z	z	z
K_DELETE		delete
K_KP0		keypad 0
K_KP1		keypad 1
K_KP2		keypad 2
K_KP3		keypad 3
K_KP4		keypad 4
K_KP5		keypad 5
K_KP6		keypad 6
K_KP7		keypad 7
K_KP8		keypad 8
K_KP9		keypad 9
K_KP_PERIOD	.	keypad period
K_KP_DIVIDE	/	keypad divide
K_KP_MULTIPLY	*	keypad multiply
K_KP_MINUS	-	keypad minus
K_KP_PLUS	+	keypad plus
K_KP_ENTER	\r	keypad enter
K_KP_EQUALS	=	keypad equals
K_UP		up arrow
K_DOWN		down arrow
K_RIGHT		right arrow
K_LEFT		left arrow
K_INSERT		insert
K_HOME		home
K_END		end
K_PAGEUP		page up
K_PAGEDOWN		page down
K_F1		F1
K_F2		F2
K_F3		F3
K_F4		F4
K_F5		F5
K_F6		F6
K_F7		F7
K_F8		F8
K_F9		F9
K_F10		F10
K_F11		F11
K_F12		F12
K_F13		F13
K_F14		F14
K_F15		F15
K_NUMLOCK		numlock
K_CAPSLOCK		capslock
K_SCROLLOCK		scrollock
K_RSHIFT		right shift
K_LSHIFT		left shift
K_RCTRL		right ctrl
K_LCTRL		left ctrl
K_RALT		right alt
K_LALT		left alt
K_RMETA		right meta
K_LMETA		left meta
K_LSUPER		left windows key
K_RSUPER		right windows key
K_MODE		mode shift
K_HELP		help
K_PRINT		print screen
K_SYSREQ		sysrq
K_BREAK		break
K_MENU		menu
K_POWER		power
K_EURO		euro

# import pygame
import pygame

# initialize game engine
pygame.init()

window_width=500
window_height=500

animation_increment=10
clock_tick_rate=10

# Open a window
size = (window_width, window_height)
screen = pygame.display.set_mode(size)

# Set title to the window
pygame.display.set_caption("Hello World")

dead=False

# Initialize values for color (RGB format)
WHITE=(255,255,255)
RED=(255,0,0)
GREEN=(0,255,0)
BLUE=(0,0,255)
BLACK=(0,0,0)

# Moving object
x_direction=0
y_direction=0
move_x_left=-3
move_x_right=3
move_y_down=3
move_y_up=-3

x_currentPos = 0
y_currentPos = 0

clock = pygame.time.Clock()

# Constants related to soldiers
soldier_head_width=10
soldier_head_height=10
soldier_start_x_position_incr=5

def draw_soldier(soldier_start_x_position, soldier_start_y_position):
    # Soldier head
    pygame.draw.ellipse(screen, BLACK, [soldier_start_x_position+soldier_start_x_position_incr,soldier_start_y_position,soldier_head_width,soldier_head_height], 0)

    # Soldier Body
    pygame.draw.line(screen, RED, [10+soldier_start_x_position, 9+soldier_start_y_position], [10+soldier_start_x_position, 20+soldier_start_y_position], 3)

    # Soldier hands
    pygame.draw.line(screen, RED, [10+soldier_start_x_position, 9+soldier_start_y_position], [5+soldier_start_x_position, 15+soldier_start_y_position], 3)
    pygame.draw.line(screen, RED, [10+soldier_start_x_position, 9+soldier_start_y_position], [15+soldier_start_x_position, 15+soldier_start_y_position], 3)

    #Soldier legs
    pygame.draw.line(screen, BLACK, [10+soldier_start_x_position, 20+soldier_start_y_position], [5+soldier_start_x_position, 26+soldier_start_y_position], 3)
    pygame.draw.line(screen, BLACK, [10+soldier_start_x_position, 20+soldier_start_y_position], [15+soldier_start_x_position, 26+soldier_start_y_position], 3)


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

        if event.type == pygame.KEYDOWN:
            if event.key == pygame.K_LEFT:
                x_direction=move_x_left
            elif event.key == pygame.K_RIGHT:
                x_direction=move_x_right
            elif event.key == pygame.K_DOWN:
                y_direction = move_y_down
            elif event.key == pygame.K_UP:
                y_direction = move_y_up

        if event.type == pygame.KEYUP:
            if event.key == pygame.K_LEFT or event.key == pygame.K_RIGHT:
                x_direction=0
            elif event.key == pygame.K_UP or event.key == pygame.K_DOWN:
                y_direction=0

        screen.fill(WHITE)
        x_currentPos += x_direction
        y_currentPos += y_direction

        if x_currentPos > window_width :
            x_currentPos=0

        if x_currentPos < 0 :
            x_currentPos = window_width-10

        if y_currentPos > window_height:
            y_currentPos=10

        if y_currentPos < 0:
            y_currentPos=window_height-10

        draw_soldier(x_currentPos, y_currentPos)


    pygame.display.flip()
    clock.tick(clock_tick_rate)

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