Welcome to Pygame Zero

Pygame Zero is for creating games without boilerplate.

It is intended for use in education, so that teachers can teach basic programming without needing to explain the Pygame API or write an event loop.

Courses

Introduction to Pygame Zero

Creating a window

First, create an empty file called intro.py.

Verify that this runs and creates a blank window by running

pgzrun intro.py

Everything in Pygame Zero is optional; a blank file is a valid Pygame Zero script!

You can quit the game by clicking on the window’s close button or by pressing Ctrl-Q (⌘-Q on Mac). If the game stops responding for any reason, you may need to terminate it by pressing Ctrl-C in your Terminal window.

Drawing a background

Next, let’s add a draw() function and set window dimensions. Pygame Zero will call this function whenever it needs to paint the screen.

In intro.py, add the following:

WIDTH = 300
HEIGHT = 300

def draw():
    screen.fill((128, 0, 0))

Re-run pgzrun intro.py and the screen should now be a reddish square!

What is this code doing?

WIDTH and HEIGHT control the width and height of your window. The code sets the window size to be 300 pixels in each dimension.

screen is a built-in that represents the window display. It has a range of methods for drawing sprites and shapes. The screen.fill() method call is filling the screen with a solid colour, specified as a (red, green, blue) colour tuple. (128, 0, 0) will be a medium-dark red. Try changing these values with numbers between 0 and 255 and see what colors you can create. You can also use a string to name a built-in colour name.

Let’s set up a sprite that we can animate.

Draw a sprite

Before we can draw anything, we’ll need to save an alien sprite to use. You can right click on this one and save it (“Save Image As…” or similar).

(This sprite has a transparency (or “alpha”) channel, which is great for games! But it’s designed for a dark background, so you may not be able to see the alien’s space helmet until it is shown in the game).

Tip

You can find lots of free sprites, including this one, on kenney.nl. This one comes from the Platformer Art Deluxe pack.

You need to save the file in the right place so that Pygame Zero can find it. Create a directory called images and save the image into it as alien.png. Both of those must be lower case. Pygame Zero will complain otherwise, to alert you to a potential cross-platform compatibility pitfall.

If you’ve done that, your project should look like this:

.
├── images/
│   └── alien.png
└── intro.py

images/ is the standard directory that Pygame Zero will look in to find your images.

There’s a built-in class called Actor that you can use to represent a graphic to be drawn to the screen.

Let’s define one now. Change the intro.py file to read:

alien = Actor('alien')
alien.pos = 100, 56

WIDTH = 500
HEIGHT = alien.height + 20

def draw():
    screen.clear()
    alien.draw()

Your alien should now be appearing on screen! By passing the string 'alien' to the Actor class, it automatically loads the sprite, and has attributes like positioning and dimensions. This allows us to set the HEIGHT of the window based on the height of the alien.

The alien.draw() method draws the sprite to the screen at its current position.

Moving the alien

Let’s set the alien off-screen; change the alien.pos line to read:

alien.topright = 0, 10

Note how you can assign to topright to move the alien actor by its top-right corner. If the right-hand edge of the alien is at 0, the alien is just offscreen to the left. Now let’s make it move. Add the following code to the bottom of the file:

def update():
    alien.left += 2
    if alien.left > WIDTH:
        alien.right = 0

Pygame Zero will call your update() function once every frame. Moving the alien a small number of pixels every frame will cause it to slide across the screen. Once it slides off the right-hand side of the screen, we reset it back to the left.

Your functions draw() and update() work in similar ways but are designed for two different purposes. The draw() function draws the current position of the alien while the update() function is used to show the alien moving on the screen.

Handling clicks

Let’s make the game do something when you click on the alien. To do this we need to define a function called on_mouse_down(). Add this to the source code:

def on_mouse_down(pos):
    if alien.collidepoint(pos):
        print("Eek!")
    else:
        print("You missed me!")

You should run the game and try clicking on and off the alien.

Pygame Zero is smart about how it calls your functions. If you don’t define your function to take a pos parameter, Pygame Zero will call it without a position. There’s also a button parameter for on_mouse_down. So we could have written:

def on_mouse_down():
    print("You clicked!")

or:

def on_mouse_down(pos, button):
    if button == mouse.LEFT and alien.collidepoint(pos):
        print("Eek!")

Sounds and images

Now let’s make the alien appear hurt. Save these files:

• alien_hurt.png - save this as alien_hurt.png in the images directory.
• eep.wav - create a directory called sounds and save this as eep.wav in that directory.

Your project should now look like this:

.
├── images/
│   └── alien.png
│   └── alien_hurt.png
├── sounds/
│   └── eep.wav
└── intro.py

sounds/ is the standard directory that Pygame Zero will look in to find your sound files.

Now let’s change the on_mouse_down function to use these new resources:

def on_mouse_down(pos):
    if alien.collidepoint(pos):
        alien.image = 'alien_hurt'
        sounds.eep.play()

Now when you click on the alien, you should hear a sound, and the sprite will change to an unhappy alien.

There’s a bug in this game though; the alien doesn’t ever change back to a happy alien (but the sound will play on each click). Let’s fix this next.

Clock

If you’re familiar with Python outside of games programming, you might know the time.sleep() method that inserts a delay. You might be tempted to write code like this:

def on_mouse_down(pos):
    if alien.collidepoint(pos):
        alien.image = 'alien_hurt'
        sounds.eep.play()
        time.sleep(1)
        alien.image = 'alien'

Unfortunately, this is not at all suitable for use in a game. time.sleep() blocks all activity; we want the game to go on running and animating. In fact we need to return from on_mouse_down, and let the game work out when to reset the alien as part of its normal processing, all the while running your draw() and update() methods.

This is not difficult with Pygame Zero, because it has a built-in Clock that can schedule functions to be called later.

First, let’s “refactor” (ie. re-organise the code). We can create functions to set the alien as hurt and also to change it back to normal:

def on_mouse_down(pos):
    if alien.collidepoint(pos):
        set_alien_hurt()


def set_alien_hurt():
    alien.image = 'alien_hurt'
    sounds.eep.play()


def set_alien_normal():
    alien.image = 'alien'

This is not going to do anything different yet. set_alien_normal() won’t be called. But let’s change set_alien_hurt() to use the clock, so that the set_alien_normal() will be called a little while after.

def set_alien_hurt():
    alien.image = 'alien_hurt'
    sounds.eep.play()
    clock.schedule_unique(set_alien_normal, 0.5)

clock.schedule_unique() will cause set_alien_normal() to be called after 0.5 second. schedule_unique() also prevents the same function being scheduled more than once, such as if you click very rapidly.

Try it, and you’ll see the alien revert to normal after 0.5 second. Try clicking rapidly and verify that the alien doesn’t revert until 0.5 second after the last click.

clock.schedule_unique() accepts both integers and float numbers for the time interval. In the tutorial we are using a float number to show this but feel free to use both to see the difference and effects the different values have.

Summary

We’ve seen how to load and draw sprites, play sounds, handle input events, and use the built-in clock.

You might like to expand the game to keep score, or make the alien move more erratically.

There are lots more features built in to make Pygame Zero easy to use. Check out the built in objects to learn how to use the rest of the API.

Migrating from Scratch

This tutorial will compare an implementation of Flappy Bird written in Scratch with one written in Pygame Zero. The Scratch and Pygame Zero programs are similar to a remarkable extent.

The Pygame Zero version can be found in Pygame Zero repository.

You can also download the Scratch 1.4 version and Scratch 3 version from the repository.

The Pygame Zero version includes scoring logic, which is omitted in the code examples on this page to make it a closer comparison.

The Python code shown below is re-arranged for clarity within the examples.

The stage

Here’s how the stage is laid out in our Scratch program:

There are just three objects, aside from the background: the bird, and the top and bottom pipes.

This corresponds to the Pygame Zero code setting these objects up as Actors:

bird = Actor('bird1', (75, 200))
pipe_top = Actor('top', anchor=('left', 'bottom'))
pipe_bottom = Actor('bottom', anchor=('left', 'top'))

In Pygame Zero we also have to ensure we draw these objects. In principle this gives a little more flexibility about how to draw the scene:

def draw():
    screen.blit('background', (0, 0))
    pipe_top.draw()
    pipe_bottom.draw()
    bird.draw()

Pipe movement

The pipes move at a constant rate irrespective of the bird. When they move off the left-hand side of the screen, they loop around to the right, and their vertical position moves at random.

In Scratch this can be achieved by creating two different scripts for the top and bottom pipe.

To summarise what’s happening here:

• The condition x position < -240 is true when a pipe is off the left-hand side of the screen, and this is the trigger to reset the pipes.
• The pipe_height variable is used to coordinate the two pipes. Because the gap between them should remain the same, we can’t pick both heights randomly. Therefore one of the scripts has this logic and the other doesn’t.
• The set y position to pipe height +/- 230 sets one pipe to be above pipe_height and the other pipe below pipe_height.

This code becomes much simpler in Pygame Zero. We could write a single function that updates both pipes. In fact I split it a different way to make it clear that the reset actions go together:

import random

WIDTH = 400
HEIGHT = 708
GAP = 130
SPEED = 3

def reset_pipes():
    pipe_gap_y = random.randint(200, HEIGHT - 200)
    pipe_top.pos = (WIDTH, pipe_gap_y - GAP // 2)
    pipe_bottom.pos = (WIDTH, pipe_gap_y + GAP // 2)

def update_pipes():
    pipe_top.left -= SPEED
    pipe_bottom.left -= SPEED
    if pipe_top.right < 0:
        reset_pipes()

A small difference here is that I can extract values that I want to re-use as “constants”, spelled in UPPERCASE. This lets me change them in one place when I want to tune the game. For example, in the code above, I could widen or narrow the gap between the two pipes simply by changing GAP.

The biggest thing that differs is that there is no forever loop in Python code. This is the big difference between Scratch and most text-based programming languages: you must update the game by one animation step and then return. Returning gives Pygame Zero a chance to do things like processing input or redrawing the screen. Loop forever and the game would just sit there, so any loops need to finish quickly.

Pygame Zero calls an update() function when it wants you to update the animation by one step, so we just need to add a call to update_pipes():

def update():
   update_pipes()

The Bird

The patterns described above for how Scratch logic translates to Python code also apply for the bird logic. Let’s look at the Python code first this time.

The code to update the bird is organised into a function called update_bird(). The first thing this function contains is some code to move the bird according to gravity:

GRAVITY = 0.3

# Initial state of the bird
bird.dead = False
bird.vy = 0

def update_bird():
    uy = bird.vy
    bird.vy += GRAVITY
    bird.y += bird.vy
    bird.x = 75

This is a simple gravity formula:

• Gravity means constant acceleration downwards.
• Acceleration is change in velocity.
• Velocity is change in position.

To represent this we need to track a variable bird.vy, which is the bird’s velocity in the y direction. This is a new variable that we are defining, not something that Pygame Zero provides for us.

• Gravity means constant acceleration downwards: GRAVITY is greater than 0.
• Acceleration is change in velocity: GRAVITY gets added to bird.vy
• Velocity is change in position: bird.vy gets added to bird.y

Note that the bird does not move horizontally! Its x position stays at 75 through the whole game. We simulate movement by moving the pipes towards it. This looks as though it’s a moving camera following the bird. So there’s no need for a vx variable in this game.

The next section makes the bird flap its wings:

if not bird.dead:
    if bird.vy < -3:
        bird.image = 'bird2'
    else:
        bird.image = 'bird1'

This checks if the bird is moving upwards or downwards. We show the bird2 image if it is moving upwards fast and the bird1 image otherwise. (-3 was picked by trial and error to make this look convincing).

The next section checks if the bird has collided with a wall:

if bird.colliderect(pipe_top) or bird.colliderect(pipe_bottom):
    bird.dead = True
    bird.image = 'birddead'

If so we set bird.dead to True. This is a boolean value meaning it is either True or False. We can use this to easily check if the bird is alive. If it isn’t alive it won’t respond to player input.

And the final section checks if the bird has fallen off the bottom (or the top) of the game screen. If so it resets the bird:

if not 0 < bird.y < 720:
    bird.y = 200
    bird.dead = False
    bird.vy = 0
    reset_pipes()

What’s reset_pipes() doing there? Because I’d organised my pipes code to be a separate function, I can just call it whenever I want to reset my walls. In this case it makes it a better game because it gives the player a chance to react when the bird moves back to its start position.

Again, this needs to be called every frame, so we add it to update():

def update():
   update_pipes()
   update_bird()

The final part of the bird logic is that it has to respond to player control. When we press a key, the bird flaps upwards. Pygame Zero will call an on_key_down() function - if you’ve defined one - whenever a key is pressed:

FLAP_VELOCITY = -6.5

def on_key_down():
    if not bird.dead:
        bird.vy = FLAP_VELOCITY

Here, if the bird is not dead, we set its vy to a negative number: in Pygame Zero this means it starts moving upwards.

You should be able to find a lot of parallels between the Python code and this Scratch code:

The biggest differences between Scratch and Pygame Zero are these:

• You cannot loop forever in Pygame Zero - just update for one frame and then return.
• The coordinates are different. In Pygame Zero, the top left of the screen is x = 0, y = 0. The x direction goes from left to right as before, but y goes down the screen! This is why GRAVITY is a positive number and FLAP_VELOCITY is a negative number in Python.
• bird.dead is a bool, so I can write code like if not bird.dead instead of dead = 0 as in Scratch.

Summary

Many of the concepts available in Scratch can be translated directly into Pygame Zero.

Here are some comparisons:

In Scratch	In Pygame Zero
change y by 1 (up)	bird.y -= 1
change y by -1 (down)	bird.y += 1
set costume to <name>	bird.image = 'name'
if dead = 0	if not bird.dead:
set dead to 0	bird.dead = False
if touching Top?	if bird.colliderect(pipe_top)
When Flag clicked… forever	Put code into the update() function.
When [any] key pressed	def on_key_down():
pick random a to b	import random to load the random module, then random.randint(a, b)
(0, 0) is the centre of the stage	(0, 0) is the top-left of the window

In some cases, the code is simpler in Python because it can be organised in a way that helps it make sense when you read it.

The power of Pygame Zero’s actors also makes the coordinate manipulation easier. We used the anchor position to position the pipes, and we were able to see if a pipe was off-screen by checking pipe_top.right < 0 rather than if x position < -240.

Reference

Event Hooks

Pygame Zero will automatically pick up and call event hooks that you define. This approach saves you from having to implement the event loop machinery yourself.

Game Loop Hooks

A typical game loop looks a bit like this:

while game_has_not_ended():
    process_input()
    update()
    draw()

Input processing is a bit more complicated, but Pygame Zero allows you to easily define the update() and draw() functions within your game module.

draw()

Called by Pygame Zero when it needs to redraw your game window.

draw() must take no arguments.

Pygame Zero attempts to work out when the game screen needs to be redrawn to avoid redrawing if nothing has changed. On each step of the game loop it will draw the screen in the following situations:

• If you have defined an update() function (see below).
• If a clock event fires.
• If an input event has been triggered.

One way this can catch you out is if you attempt to modify or animate something within the draw function. For example, this code is wrong: the alien is not guaranteed to continue moving across the screen:

def draw():
    alien.left += 1
    alien.draw()

The correct code uses update() to modify or animate things and draw simply to paint the screen:

def draw():
    alien.draw()

def update():
    alien.left += 1

update() or update(dt)

Called by Pygame Zero to step your game logic. This will be called repeatedly, 60 times a second.

There are two different approaches to writing an update function.

In simple games you can assume a small time step (a fraction of a second) has elapsed between each call to update(). Perhaps you don’t even care how big that time step is: you can just move objects by a fixed number of pixels per frame (or accelerate them by a fixed constant, etc.)

A more advanced approach is to base your movement and physics calculations on the actual amount of time that has elapsed between calls. This can give smoother animation, but the calculations involved can be harder and you must take more care to avoid unpredictable behaviour when the time steps grow larger.

To use a time-based approach, you can change the update function to take a single parameter. If your update function takes an argument, Pygame Zero will pass it the elapsed time in seconds. You can use this to scale your movement calculations.

Event Handling Hooks

Similar to the game loop hooks, your Pygame Zero program can respond to input events by defining functions with specific names.

Somewhat like in the case of update(), Pygame Zero will inspect your event handler functions to determine how to call them. So you don’t need to make your handler functions take arguments. For example, Pygame Zero will be happy to call any of these variations of an on_mouse_down function:

def on_mouse_down():
    print("Mouse button clicked")

def on_mouse_down(pos):
    print("Mouse button clicked at", pos)

def on_mouse_down(button):
    print("Mouse button", button, "clicked")

def on_mouse_down(pos, button):
    print("Mouse button", button, "clicked at", pos)

It does this by looking at the names of the parameters, so they must be spelled exactly as above. Each event hook has a different set of parameters that you can use, as described below.

on_mouse_down([pos][, button])

Called when a mouse button is depressed.

Parameters:

• pos – A tuple (x, y) that gives the location of the mouse pointer when the button was pressed.
• button – A mouse enum value indicating the button that was pressed.

on_mouse_up([pos][, button])

Called when a mouse button is released.

Parameters:

• pos – A tuple (x, y) that gives the location of the mouse pointer when the button was released.
• button – A mouse enum value indicating the button that was released.

on_mouse_move([pos][, rel][, buttons])

Called when the mouse is moved.

Parameters:

• pos – A tuple (x, y) that gives the location that the mouse pointer moved to.
• rel – A tuple (delta_x, delta_y) that represent the change in the mouse pointer’s position.
• buttons – A set of mouse enum values indicating the buttons that were depressed during the move.

To handle mouse drags, use code such as the following:

def on_mouse_move(rel, buttons):
    if mouse.LEFT in buttons:
        # the mouse was dragged, do something with `rel`
        ...

on_key_down([key][, mod][, unicode])

Called when a key is depressed.

Parameters:

• key – An integer indicating the key that was pressed (see below).
• unicode – Where relevant, the character that was typed. Not all keys will result in printable characters - many may be control characters. In the event that a key doesn’t correspond to a Unicode character, this will be the empty string.
• mod – A bitmask of modifier keys that were depressed.

on_key_up([key][, mod])

Called when a key is released.

Parameters:

• key – An integer indicating the key that was released (see below).
• mod – A bitmask of modifier keys that were depressed.

on_music_end()

Called when a music track finishes.

Note that this will not be called if the track is configured to loop.

Buttons and Keys

Built-in objects mouse and keys can be used to determine which buttons or keys were pressed in the above events.

Note that mouse scrollwheel events appear as button presses with the below WHEEL_UP/WHEEL_DOWN button constants.

class mouse

A built-in enumeration of buttons that can be received by the on_mouse_* handlers.

LEFT

MIDDLE

RIGHT

WHEEL_UP

WHEEL_DOWN

class keys

A built-in enumeration of keys that can be received by the on_key_* handlers.

BACKSPACE

TAB

CLEAR

RETURN

PAUSE

ESCAPE

SPACE

EXCLAIM

QUOTEDBL

HASH

DOLLAR

AMPERSAND

QUOTE

LEFTPAREN

RIGHTPAREN

ASTERISK

PLUS

COMMA

MINUS

PERIOD

SLASH

K_0

K_1

K_2

K_3

K_4

K_5

K_6

K_7

K_8

K_9

COLON

SEMICOLON

LESS

EQUALS

GREATER

QUESTION

AT

LEFTBRACKET

BACKSLASH

RIGHTBRACKET

CARET

UNDERSCORE

BACKQUOTE

A

B

C

D

E

F

G

H

I

J

K

L

M

N

O

P

Q

R

S

T

U

V

W

X

Y

Z

DELETE

KP0

KP1

KP2

KP3

KP4

KP5

KP6

KP7

KP8

KP9

KP_PERIOD

KP_DIVIDE

KP_MULTIPLY

KP_MINUS

KP_PLUS

KP_ENTER

KP_EQUALS

UP

DOWN

RIGHT

LEFT

INSERT

HOME

END

PAGEUP

PAGEDOWN

F1

F2

F3

F4

F5

F6

F7

F8

F9

F10

F11

F12

F13

F14

F15

NUMLOCK

CAPSLOCK

SCROLLOCK

RSHIFT

LSHIFT

RCTRL

LCTRL

RALT

LALT

RMETA

LMETA

LSUPER

RSUPER

MODE

HELP

PRINT

SYSREQ

BREAK

MENU

POWER

EURO

LAST

Additionally you can access a set of constants that represent modifier keys:

class keymods

Constants representing modifier keys that may have been depressed during an on_key_up/on_key_down event.

LSHIFT

RSHIFT

SHIFT

LCTRL

RCTRL

CTRL

LALT

RALT

ALT

LMETA

RMETA

META

NUM

CAPS

MODE

Built-in Objects

Pygame Zero provides useful built-in objects to help you make games easily.

Screen

Text Formatting

The Screen’s draw.text() method has a very rich set of methods for position and formatting of text. Some examples:

screen.draw.text("Text color", (50, 30), color="orange")
screen.draw.text("Font name and size", (20, 100), fontname="boogaloo", fontsize=60)
screen.draw.text("Positioned text", topright=(840, 20))
screen.draw.text("Allow me to demonstrate wrapped text.", (90, 210), width=180, lineheight=1.5)
screen.draw.text("Outlined text", (400, 70), owidth=1.5, ocolor=(255,255,0), color=(0,0,0))
screen.draw.text("Drop shadow", (640, 110), shadow=(2,2), scolor="#202020")
screen.draw.text("Color gradient", (540, 170), color="red", gcolor="purple")
screen.draw.text("Transparency", (700, 240), alpha=0.1)
screen.draw.text("Vertical text", midleft=(40, 440), angle=90)
screen.draw.text("All together now:\nCombining the above options",
    midbottom=(427,460), width=360, fontname="boogaloo", fontsize=48,
    color="#AAFF00", gcolor="#66AA00", owidth=1.5, ocolor="black", alpha=0.8)

In its simplest usage, screen.draw.text requires the string you want to draw, and the position. You can either do this by passing coordinates as the second argument (which is the top left of where the text will appear), or use the positioning keyword arguments (described later):

screen.draw.text("hello world", (20, 100))

screen.draw.text takes many optional keyword arguments, described below.

Font name and size

Fonts are loaded from a directory named fonts, in a similar way to the handling of images and sounds. Fonts must be in .ttf format. For example:

screen.draw.text("hello world", (100, 100), fontname="Viga", fontsize=32)

Keyword arguments:

• fontname: filename of the font to draw. By default, use the system font.
• fontsize: size of the font to use, in pixels. Defaults to 24.
• antialias: whether to render with antialiasing. Defaults to True.

Color and background color

screen.draw.text("hello world", (100, 100), color=(200, 200, 200), background="gray")

Keyword arguments:

• color: foreground color to use. Defaults to white.
• background: background color to use. Defaults to None.

color (as well as background, ocolor, scolor, and gcolor) can be an (r, g, b) sequence such as (255,127,0), a pygame.Color object, a color name such as "orange", an HTML hex color string such as "#FF7F00", or a string representing a hex color number such as "0xFF7F00".

background can also be None, in which case the background is transparent. Unlike pygame.font.Font.render, it’s generally not more efficient to set a background color when calling screen.draw.text. So only specify a background color if you actually want one.

Colors with alpha transparency are not supported (except for the special case of invisible text with outlines or drop shadows - see below). See the alpha keyword argument for transparency.

Positioning

screen.draw.text("hello world", centery=50, right=300)
screen.draw.text("hello world", midtop=(400, 0))

Keyword arguments:

top left bottom right
topleft bottomleft topright bottomright
midtop midleft midbottom midright
center centerx centery

Positioning keyword arguments behave like the corresponding properties of pygame.Rect. Either specify two arguments, corresponding to the horizontal and vertical positions of the box, or a single argument that specifies both.

If the position is overspecified (e.g. both left and right are given), then extra specifications will be (arbitrarily but deterministically) discarded. For constrained text, see the section on screen.draw.textbox below.

Word wrap

screen.draw.text("splitting\nlines", (100, 100))
screen.draw.text("splitting lines", (100, 100), width=60)

Keyword arguments:

• width: maximum width of the text to draw, in pixels. Defaults to None.
• widthem: maximum width of the text to draw, in font-based em units. Defaults to None.
• lineheight: vertical spacing between lines, in units of the font’s default line height. Defaults to 1.0.

screen.draw.text will always wrap lines at newline (\n) characters. If width or widthem is set, it will also try to wrap lines in order to keep each line shorter than the given width. The text is not guaranteed to be within the given width, because wrapping only occurs at space characters, so if a single word is too long to fit on a line, it will not be broken up. Outline and drop shadow are also not accounted for, so they may extend beyond the given width.

You can prevent wrapping on a particular space with non-breaking space characters (\u00A0).

Text alignment

screen.draw.text("hello\nworld", bottomright=(500, 400), align="left")

Keyword argument:

• align: horizontal positioning of lines with respect to each other. Defaults to None.

align determines how lines are positioned horizontally with respect to each other, when more than one line is drawn. Valid values for align are the strings "left", "center", or "right", a numerical value between 0.0 (for left alignment) and 1.0 (for right alignment), or None.

If align is None, the alignment is determined based on other arguments, in a way that should be what you want most of the time. It depends on any positioning arguments (topleft, centerx, etc.), anchor, and finally defaults to "left". I suggest you generally trust the default alignment, and only specify align if something doesn’t look right.

Outline

screen.draw.text("hello world", (100, 100), owidth=1, ocolor="blue")

Keyword arguments:

• owidth: outline thickness, in outline units. Defaults to None.
• ocolor: outline color. Defaults to "black".

The text will be outlined if owidth is specified. The outlining is a crude manual method, and will probably look bad at large sizes. The units of owidth are chosen so that 1.0 is a good typical value for outlines. Specifically, they’re the font size divided by 24.

As a special case, setting color to a transparent value (e.g. (0,0,0,0)) while using outilnes will cause the text to be invisible, giving a hollow outline. (This feature is not compatible with gcolor.)

Valid values for ocolor are the same as for color.

Drop shadow

screen.draw.text("hello world", (100, 100), shadow=(1.0,1.0), scolor="blue")

Keyword arguments:

• shadow: (x,y) values representing the drop shadow offset, in shadow units. Defaults to None.
• scolor: drop shadow color. Defaults to "black".

The text will have a drop shadow if shadow is specified. It must be set to a 2-element sequence representing the x and y offsets of the drop shadow, which can be positive, negative, or 0. For example, shadow=(1.0,1.0) corresponds to a shadow down and to the right of the text. shadow=(0,-1.2) corresponds to a shadow higher than the text.

The units of shadow are chosen so that 1.0 is a good typical value for the offset. Specifically, they’re the font size divided by 18.

As a special case, setting color to a transparent value (e.g. (0,0,0,0)) while using drop shadow will cause the text to be invisible, giving a hollow shadow. (This feature is not compatible with gcolor.)

Valid values for scolor are the same as for color.

Gradient color

screen.draw.text("hello world", (100, 100), color="black", gcolor="green")

Keyword argument:

• gcolor: Lower gradient stop color. Defaults to None.

Specify gcolor to color the text with a vertical color gradient. The text’s color will be color at the top and gcolor at the bottom. Positioning of the gradient stops and orientation of the gradient are hard coded and cannot be specified.

Alpha transparency

screen.draw.text("hello world", (100, 100), alpha=0.5)

Keyword argument:

• alpha: alpha transparency value, between 0 and 1. Defaults to 1.0.

In order to maximize reuse of cached transparent surfaces, the value of alpha is rounded.

Anchored positioning

screen.draw.text("hello world", (100, 100), anchor=(0.3,0.7))

Keyword argument:

• anchor: a length-2 sequence of horizontal and vertical anchor fractions. Defaults to (0.0, 0.0).

anchor specifies how the text is anchored to the given position, when no positioning keyword arguments are passed. The two values in anchor can take arbitrary values between 0.0 and 1.0. An anchor value of (0,0), the default, means that the given position is the top left of the text. A value of (1,1) means the given position is the bottom right of the text.

Rotation

screen.draw.text("hello world", (100, 100), angle=10)

Keyword argument:

• angle: counterclockwise rotation angle in degrees. Defaults to 0.

Positioning of rotated surfaces is tricky. When drawing rotated text, the anchor point, the position you actually specify, remains fixed, and the text rotates around it. For instance, if you specify the top left of the text to be at (100, 100) with an angle of 90, then the Surface will actually be drawn so that its bottom left is at (100, 100).

If you find that confusing, try specifying the center. If you anchor the text at the center, then the center will remain fixed, no matter how you rotate it.

In order to maximize reuse of cached rotated surfaces, the value of angle is rounded to the nearest multiple of 3 degrees.

Constrained text

screen.draw.textbox("hello world", (100, 100, 200, 50))

screen.draw.textbox requires two arguments: the text to be drawn, and a pygame.Rect or a Rect-like object to stay within. The font size will be chosen to be as large as possible while staying within the box. Other than fontsize and positional arguments, you can pass all the same keyword arguments to screen.draw.textbox as to screen.draw.text.

The screen object represents your game screen.

It is a thin wrapper around a Pygame surface that allows you to easily draw images to the screen (“blit” them).

class Screen

surface

The raw Pygame surface that represents the screen buffer. You can use this for advanced graphics operations.

bounds()

New in version 1.3.

Return a ZRect representing the bounds of the screen.

clear()

Reset the screen to black.

fill((red, green, blue)[, gcolor=(r, g, b)])

Fill the screen with a solid color.

New in version 1.3: If gcolor is given then fill with a gradient, from color at the top of the screen to gcolor at the bottom.

blit(image, (left, top))

Draw the image to the screen at the given position.

blit() accepts either a Surface or a string as its image parameter. If image is a str then the named image will be loaded from the images/ directory.

draw.line(start, end, (r, g, b), width=1)

Draw a line from start to end with a certain line width.

draw.circle(pos, radius, (r, g, b), width=1)

Draw the outline of a circle with a certain line width.

draw.filled_circle(pos, radius, (r, g, b))

Draw a filled circle.

draw.rect(rect, (r, g, b), width=1)

Draw the outline of a rectangle with a certain line width.

Takes a Rect.

draw.filled_rect(rect, (r, g, b))

Draw a filled rectangle.

draw.text(text, [pos, ]**kwargs)

Draw text.

There’s an extremely rich API for positioning and formatting text; see Text Formatting for full details.

draw.textbox(text, rect, **kwargs)

Draw text, sized to fill the given Rect.

There’s an extremely rich API for formatting text; see Text Formatting for full details.

Tip

All of the colours can be specified as (r, g, b) tuples, or by name, using one of Pygame’s colour names

Rect

The Pygame Rect class is available as a built in. This can be used in a variety of ways, from detecting clicks within a region to drawing a box onto the screen:

For example, you can draw a box with:

RED = 200, 0, 0
BOX = Rect((20, 20), (100, 100))

def draw():
    screen.draw.rect(BOX, RED)

Resource Loading

The images and sounds objects can be used to load images and sounds from files stored in the images and sounds subdirectories respectively. Pygame Zero will handle loading of these resources on demand and will cache them to avoid reloading them.

You generally need to ensure that your images are named with lowercase letters, numbers and underscores only. They also have to start with a letter.

File names like these will work well with the resource loader:

alien.png
alien_hurt.png
alien_run_7.png

These will not work:

3.png
3degrees.png
my-cat.png
sam's dog.png

The resource loader caches loaded images and sounds. To clear the cache (for instance, if you are running into memory issues), use the unload() and unload_all() functions.

Example:

cow = Actor('cow')
loader.images.unload('cow')  # clears the cache of cow.png
loader.images.unload_all()  # clears all cached image files

Images

Pygame Zero can load images in .png, .gif, and .jpg formats. PNG is recommended: it will allow high quality images with transparency.

We need to ensure an images directory is set up. If your project contains the following files:

space_game.py
images/alien.png

Then space_game.py could draw the ‘alien’ sprite to the screen with this code:

def draw():
    screen.clear()
    screen.blit('alien', (10, 10))

The name passed to blit() is the name of the image file within the images directory, without the file extension.

Or using the Actors API,

alien = Actor('alien')

def draw():
    alien.draw()

There are some restrictions on the file names in both cases: they may only contain lowercase latin letters, numbers and underscores. This is to prevent compatibility problems when your game is played on a different operating system that has different case sensitivity.

Image Surfaces

You can also load images from the images directory using the images object. This allows you to work with the image data itself, query its dimensions and so on:

forest = []
for i in range(5):
    forest.append(
        Actor('tree', topleft=(images.tree.get_width() * i, 0))
    )

Each loaded image is a Pygame Surface. You will typically use screen.blit(...) to draw this to the screen. It also provides handy methods to query the size of the image in pixels:

class Surface

get_width()

Returns the width of the image in pixels.

get_height()

Returns the height of the image in pixels.

get_size()

Returns a tuple (width, height) indicating the size in pixels of the surface.

get_rect()

Get a Rect that is pre-populated with the bounds of the image if the image was located at the origin.

Effectively this is equivalent to:

Rect((0, 0), image.get_size())

Sounds

Pygame Zero can load sounds in .wav and .ogg formats. WAV is great for small sound effects, while OGG is a compressed format that is more suited to music. You can find free .ogg and .wav files online that can be used in your game.

We need to ensure a sounds directory is set up. If your project contains the following files:

drum_kit.py
sounds/drum.wav

Then drum_kit.py could play the drum sound whenever the mouse is clicked with this code:

def on_mouse_down():
    sounds.drum.play()

Each loaded sound is a Pygame Sound, and has various methods to play and stop the sound as well as query its length in seconds:

class Sound

play()

Play the sound.

play(loops)

Play the sound, but loop it a number of times.

Parameters:loops – The number of times to loop. If you pass -1 as the number of times to loop, the sound will loop forever (or until you call Sound.stop()

stop()

Stop playing the sound.

get_length()

Get the duration of the sound in seconds.

You should avoid using the sounds object to play longer pieces of music. Because the sounds sytem will fully load the music into memory before playing it, this can use a lot of memory, as well as introducing a delay while the music is loaded.

Music

New in version 1.1.

Warning

The music API is experimental and may be subject to cross-platform portability issues.

In particular:

• MP3 may not be available on some Linux distributions.
• Some OGG Vorbis files seem to hang Pygame with 100% CPU.

In the case of the latter issue, the problem may be fixed by re-encoding (possibly with a different encoder).

A built-in object called music provides access to play music from within a music/ directory (alongside your images/ and sounds/ directories, if you have them). The music system will load the track a little bit at a time while the music plays, avoiding the problems with using sounds to play longer tracks.

Another difference to the sounds system is that only one music track can be playing at a time. If you play a different track, the previously playing track will be stopped.

music.play(name)

Play a music track from the given file. The track will loop indefinitely.

This replaces the currently playing track and cancels any tracks previously queued with queue().

You do not need to include the extension in the track name; for example, to play the file handel.mp3 on a loop:

music.play('handel')

music.play_once(name)

Similar to play(), but the music will stop after playing through once.

music.queue(name)

Similar to play_once(), but instead of stopping the current music, the track will be queued to play after the current track finishes (or after any other previously queued tracks).

music.stop()

Stop the music.

music.pause()

Pause the music temporarily. It can be resumed by calling unpause().

music.unpause()

Unpause the music.

music.is_playing()

Returns True if the music is playing (and is not paused), False otherwise.

music.fadeout(duration)

Fade out and eventually stop the current music playback.

Parameters:duration – The duration in seconds over which the sound will be faded out. For example, to fade out over half a second, call music.fadeout(0.5).

music.set_volume(volume)

Set the volume of the music system.

This takes a number between 0 (meaning silent) and 1 (meaning full volume).

music.get_volume()

Get the current volume of the music system.

If you have started a music track playing using music.play_once(), you can use the on_music_end() hook to do something when the music ends - for example, to pick another track at random.

Clock

Often when writing a game, you will want to schedule some game event to occur at a later time. For example, we may want a big boss alien to appear after 60 seconds. Or perhaps a power-up will appear every 20 seconds.

More subtle are the situations when you want to delay some action for a shorter period. For example you might have a laser weapon that takes 1 second to charge up.

We can use the clock object to schedule a function to happen in the future.

Let’s start by defining a function fire_laser that we want to run in the future:

def fire_laser():
    lasers.append(player.pos)

Then when the fire button is pressed, we will ask the clock to call it for us after exactly 1 second:

def on_mouse_down():
    clock.schedule(fire_laser, 1.0)

Note that fire_laser is the function itself; without parentheses, it is not being called here! The clock will call it for us.

(It is a good habit to write out times in seconds with a decimal point, like 1.0. This makes it more obvious when you are reading it back, that you are referring to a time value and not a count of things.)

clock provides the following useful methods:

class Clock

schedule(callback, delay)

Schedule callback to be called after the given delay.

Repeated calls will schedule the callback repeatedly.

Parameters:

• callback – A callable that takes no arguments.
• delay – The delay, in seconds, before the function should be called.

schedule_unique(callback, delay)

Schedule callback to be called once after the given delay.

If callback was already scheduled, cancel and reschedule it. This applies also if it was scheduled multiple times: after calling schedule_unique, it will be scheduled exactly once.

Parameters:

• callback – A callable that takes no arguments.
• delay – The delay, in seconds, before the function should be called.

schedule_interval(callback, interval)

Schedule callback to be called repeatedly.

Parameters:

• callback – A callable that takes no arguments.
• interval – The interval in seconds between calls to callback.

unschedule(callback)

Unschedule callback if it has been previously scheduled (either because it has been scheduled with schedule() and has not yet been called, or because it has been scheduled to repeat with schedule_interval().

Note that the Pygame Zero clock only holds weak references to each callback you give it. It will not fire scheduled events if the objects and methods are not referenced elsewhere. This can help prevent the clock keeping objects alive and continuing to fire unexpectedly after they are otherwise dead.

The downside to the weak references is that you won’t be able to schedule lambdas or any other object that has been created purely to be scheduled. You will have to keep a reference to the object.

Actors

Once you have many images moving around in a game it can be convenient to have something that holds in one place the image and where it is on screen. We’ll call each moving image on screen an Actor. You can create an actor by supplying at least an image name (from the images folder above). To draw the alien talked about above:

alien = Actor('alien', (50, 50))

def draw():
    screen.clear()
    alien.draw()

You can move the actor around by setting its pos attribute in an update:

def update():
    if keyboard.left:
        alien.x -= 1
    elif keyboard.right:
        alien.x += 1

And you may change the image used to draw the actor by setting its image attribute to some new image name:

alien.image = 'alien_hurt'

Actors have all the same attributes and methods as Rect, including methods like .colliderect() which can be used to test whether two actors have collided.

Positioning Actors

If you assign a new value to one of the position attributes then the actor will be moved. For example:

alien.right = WIDTH

will position the alien so its right-hand side is set to WIDTH.

Similarly, you can also set the initial position of the actor in the constructor, by passing one of these as a keyword argument: pos, topleft, topright, bottomleft, bottomright, midtop, midleft, midright, midbottom or center:

This can be done during creation or by assigning a pair of x, y co-ordinates. For example:

WIDTH = 200
HEIGHT = 200

alien = Actor('alien', center=(100,100))

def draw():
    screen.clear()
    alien.draw()

Changing center=(100, 100) to midbottom=(100, 200) gives you:

If you don’t specify an initial position, the actor will initially be positioned in the top-left corner (equivalent to topleft=(0, 0)).

Anchor point

Actors have an “anchor position”, which is a convenient way to position the actor in the scene. By default, the anchor position is the center, so the .pos attribute refers to the center of the actor (and so do the x and y coordinates). It’s common to want to set the anchor point to another part of the sprite (perhaps the feet - so that you can easily set the Actor to be “standing on” something):

alien = Actor('alien', anchor=('center', 'bottom'))
spaceship = Actor('spaceship', anchor=(10, 50))

anchor is specified as a tuple (xanchor, yanchor), where the values can be floats or the strings left, center/middle, right, top or bottom as appropriate.

Rotation

New in version 1.2.

The .angle attribute of an Actor controls the rotation of the sprite, in degrees, anticlockwise (counterclockwise).

The centre of rotation is the Actor’s anchor point.

Note that this will change the width and height of the Actor.

For example, to make an asteroid sprite spinning slowly anticlockwise in space:

asteroid = Actor('asteroid', center=(300, 300))

def update():
    asteroid.angle += 1

To have it spin clockwise, we’d change update() to:

def update():
    asteroid.angle -= 1

As a different example, we could make an actor ship always face the mouse pointer. Because angle_to() returns 0 for “right”, the sprite we use for “ship” should face right:

ship = Actor('ship')

def on_mouse_move(pos):
    ship.angle = ship.angle_to(pos)

Remember that angles loop round, so 0 degrees == 360 degrees == 720 degrees. Likewise -180 degrees == 180 degrees.

Distance and angle to

New in version 1.2.

Actors have convenient methods for calculating their distance or angle to other Actors or (x, y) coordinate pairs.

Actor.distance_to(target)

Return the distance from this actor’s position to target, in pixels.

Actor.angle_to(target)

Return the angle from this actor’s position to target, in degrees.

This will return a number between -180 and 180 degrees. Right is 0 degrees and the angles increase going anticlockwise.

Therefore:

• Left is 180 degrees.
• Up is 90 degrees.
• Down is -90 degrees.

Transparency

New in version 1.3.

In some cases it is useful to make an Actor object partially transparent. This can be used to fade it in or out, or to indicate that it is “disabled”.

The .opacity attribute of an Actor controls how transparent or opaque it is.

• When an actor is not at all transparent, we say it is “opaque” and it has opacity of 1.0, and you can’t see through it at all.
• When an actor is completely transparent, it has an opacity of 0.0. This will make it completely invisible.

To make an actor that is half-transparent (like a ghost), you could write:

ghost = Actor('ghost')
ghost.opacity = 0.5

This diagram shows the scale; the grey checkerboard is used to give the sense of transparency:

Tip

The order in which you draw overlapping transparent objects still matters. A ghost seen through a window looks slightly different to a window seen through a ghost.

The Keyboard

You probably noticed that we used the keyboard in the above code. If you’d like to know what keys are pressed on the keyboard, you can query the attributes of the keyboard builtin. If, say, the left arrow is held down, then keyboard.left will be True, otherwise it will be False.

There are attributes for every key; some examples:

keyboard.a  # The 'A' key
keyboard.left  # The left arrow key
keyboard.rshift  # The right shift key
keyboard.kp0  # The '0' key on the keypad
keyboard.k_0  # The main '0' key

The full set of key constants is given in the Buttons and Keys documentation, but the attributes are lowercase, because these are variables not constants.

Deprecated since version 1.1: Uppercase and prefixed attribute names (eg. keyboard.LEFT or keyboard.K_a) are now deprecated; use lowercase attribute names instead.

New in version 1.1: You can now also query the state of the keys using the keyboard constants themselves:

keyboard[keys.A]  # True if the 'A' key is pressed
keyboard[keys.SPACE]  # True if the space bar is pressed

Animations

You can animate most things in pygame using the builtin animate(). For example, to move an Actor from its current position on the screen to the position (100, 100):

animate(alien, pos=(100, 100))

animate(object, tween='linear', duration=1, on_finished=None, **targets)

Animate the attributes on object from their current value to that specified in the targets keywords.

Parameters:

• tween – The type of tweening to use.
• duration – The duration of the animation, in seconds.
• on_finished – Function called when the animation finishes.
• targets – The target values for the attributes to animate.

The tween argument can be one of the following:

‘linear’	Animate at a constant speed from start to finish
‘accelerate’	Start slower and accelerate to finish
‘decelerate’	Start fast and decelerate to finish
‘accel_decel’	Accelerate to mid point and decelerate to finish
‘in_elastic’	Give a little wobble at the end
‘out_elastic’	Have a little wobble at the start
‘in_out_elastic’	Have a wobble at both ends
‘bounce_end’	Accelerate to the finish and bounce there
‘bounce_start’	Bounce at the start
‘bounce_start_end’	Bounce at both ends

The animate() function returns an Animation instance:

class Animation

stop(complete=False)

Stop the animation, optionally completing the transition to the final property values.

Parameters:complete – Set the animated attribute to the target value.

running

This will be True if the animation is running. It will be False when the duration has run or the stop() method was called before then.

on_finished

You may set this attribute to a function which will be called when the animation duration runs out. The on_finished argument to animate() also sets this attribute. It is not called when stop() is called. This function takes no arguments.

Tone Generator

New in version 1.2.

Pygame Zero can play tones using a built-in synthesizer.

tone.play(pitch, duration)

Play a note at the given pitch for the given duration.

Duration is in seconds.

The pitch can be specified as a number in which case it is the frequency of the note in hertz.

Alternatively, the pitch can be specified as a string representing a note name and octave. For example:

• 'E4' would be E in octave 4.
• 'A#5' would be A-sharp in octave 5.
• 'Bb3' would be B-flat in octave 3.

Creating notes, particularly long notes, takes time - up to several milliseconds. You can create your notes ahead of time so that this doesn’t slow your game down while it is running:

tone.create(pitch, duration)

Create and return a Sound object.

The arguments are as for play(), above.

This could be used in a Pygame Zero program like this:

beep = tone.create('A3', 0.5)

def on_mouse_down():
    beep.play()

Data Storage

The storage object behaves just like a Python dictionary but its contents are preserved across game sessions. The values you assign to storage will be saved as JSON, which means you can only store certain types of objects in it: list/tuple, dict, str, float/int, bool, and None.

The storage for a game is initially empty. Your code will need to handle the case that values are loaded as well as the case that no values are found.

A tip is to use setdefault(), which inserts a default if there is no value for the key, but does nothing if there is.

For example, we could write:

storage.setdefault('highscore', 0)

After this line is executed, storage['highscore'] will contain a value - 0 if there was no value loaded, or the loaded value otherwise. You could add all of your setdefault lines towards the top of your game, before anything else looks at storage:

storage.setdefault('level', 1)
storage.setdefault('player_name', 'Anonymous')
storage.setdefault('inventory', [])

Now, during gameplay we can update some values:

if player.colliderect(mushroom):
    score += 5
    if score > storage['highscore']:
        storage['highscore'] = score

You can read them back at any time:

def draw():
    ...
    screen.draw.text('Highscore: ' + storage['highscore'], ...)

…and of course, they’ll be preserved when the game next launches.

These are some of the most useful methods of storage:

class Storage(dict)

storage[key] = value

Set a value in the storage.

storage[key]

Get a value from the storage. Raise KeyError if there is no such key in the storage.

setdefault(key, default)

Insert a default value into the storage, only if no value already exists for this key.

get(key, default=None)

Get a value from the storage. If there is no such key, return default, or None if no default was given.

clear()

Remove all stored values. Use this if you get into a bad state.

save()

Saves the data to disk now. You don’t usually need to call this, unless you’re planning on using load() to reload a checkpoint, for example.

load()

Reload the contents of the storage with data from the save file. This will replace any existing data in the storage.

path

The actual path to which the save data will be written.

Caution

As you make changes to your game, storage could contain values that don’t work with your current code. You can either check for this, or call .clear() to remove all old values, or delete the save game file.

Tip

Remember to check that your game still works if the storage is empty!

User Guide

Installing Pygame Zero

On desktop systems

pip install pgzero

This will also install Pygame. Pre-compiled Pygame packages are available to pip for Windows & Linux (32-bit and 64-bit), and for Mac OS (64-bit only). If you have a different system, you’ll need to find a way to install pygame first. Make sure you are using Python 3 not Python 2.

Mac

In a Terminal window, type

pip install pgzero

Note that there are currently no Wheels for Pygame that support python 3.4 for Mac, so you will need to upgrade Python to >=3.6 (or use python 2.7) in order to be able to install pygame. For a list of available Wheels, please visit pyPI_

Linux

In a terminal window, type

sudo pip install pgzero

Some Linux systems call it pip3; if the above command printed something like sudo: pip: command not found then try:

sudo pip3 install pgzero

Sometimes pip is not installed and needs to be installed. If so try this before running the above commands again:

sudo python3 -m ensurepip

On Raspberry Pi

pgzero has been installed by default since the release of Raspbian Jessie in September 2015!

For flake8/pyflakes

Checkers like Pyflakes are unaware of Pygame Zero’s extra builtins.

If you use flake8, you can add Pygame Zero’s list of builtins to your flake8 configuration file:

[flake8]
builtins = Actor,Rect,ZRect,animate,clock,exit,images,keyboard,keymods,keys,mouse,music,screen,sounds,storage,tone

If you use pyflakes directly then this is configured using the environment variable $PYFLAKES_BUILTINS. On Linux and Mac you could write this in your terminal or put it in your shell configuration file (like ~/.bashrc)

PYFLAKES_BUILTINS=Actor,Rect,ZRect,animate,clock,exit,images,keyboard,keymods,keys,mouse,music,screen,sounds,storage,tone
export PYFLAKES_BUILTINS

On Windows:

set PYFLAKES_BUILTINS=Actor,Rect,ZRect,animate,clock,exit,images,keyboard,keymods,keys,mouse,music,screen,sounds,storage,tone

Running Pygame Zero in IDLE and other IDEs

New in version 1.2.

Pygame Zero is usually run using a command such as:

pgzrun my_program.py

Certain programs, such as integrated development environments like IDLE and Edublocks, will only run python, not pgzrun.

Pygame Zero includes a way of writing a full Python program that can be run using python. To do it, put

import pgzrun

as the very first line of the Pygame Zero program, and put

pgzrun.go()

as the very last line.

Example

Here is a Pygame Zero program that draws a circle. You can run this by pasting it into IDLE:

import pgzrun


WIDTH = 800
HEIGHT = 600

def draw():
    screen.clear()
    screen.draw.circle((400, 300), 30, 'white')


pgzrun.go()

Examples

Pygame Zero has a collection of examples which you can use to learn by reading or modifying the code of the game. You can also play with them! These examples aren’t provided with a normal installation of Pygame Zero but they’re available in the source code repository. To download them, follow the following steps:

• Download the source code of Pygame Zero on the GitHub repository by clicking in the big green button and choosing Download ZIP
• Copy the examples folder whatever you want.
• Delete the ZIP and the source code if you want to save space on your disk.

Now you can play with them as another game that you might created. For example, to run the pong game, you should run:

pgzrun examples/pong/pong.py

Reading & editing the source code is a great way to learn to code, so start hacking the code!

List of example games

Asteroids

To play, run:

pgzrun examples/asteroids/main.py

Basic

This a collection of simple examples that you can use to learn who to use key parts of Pygame Zero. Some of them are examples explained in the documentation.

Flappybird

To play, run:

pgzrun examples/flappybird/flappybird.py

Lander

To play, run:

pgzrun examples/lander/lander.py

Memory

To play, run:

pgzrun examples/memory/memory.py

Mines

To play, run:

pgzrun examples/mines/mines.py

Pong

To play, run:

pgzrun examples/pong/pong.py

Snake

To play, run:

pgzrun examples/snake/snake.py

Tetra puzzle

To play, run:

pgzrun examples/tetra_puzzle/main.py

Tron

To play, run:

pgzrun examples/tron/tron.py

Tutorials and Resources

Here are some tutorials and learning resources which use Pygame Zero.

Books

• Coding Games in Python (DK) - teaches programming in Python from scratch with Pygame Zero and bright, colourful illustrations.
• Code the Classics (Raspberry Pi Press) - covers the history of classic computer games and explains how to make them with Pygame Zero.
• Mission Python (No Starch Press) - takes you through the process of writing one larger game with Pygame Zero.

Online Tutorials

• Simple Game Tutorials is a collection of step-by-step tutorials which guide you through the process of making some simple games.
• Coding Games with Pygame Zero and Python - teaches programming in Python for complete beginners, moving into several complete examples.
• Game Development with Pygame Zero - walks through creating several small, fun games.

Magazines

• MagPi, the Raspberry Pi magazine, has covered Pygame Zero several times. MagPi is available in print but is also free to download online.
• Wireframe, also from Raspberry Pi, and also free to download online, is a magazine focused on games, game development, and the game industry, and most issues contain Pygame Zero examples.

Video Tutorials

There are numerous Pygame Zero tutorial videos on YouTube; here are some:

• A brief introduction to Pygame Zero (Neil Muller)
• How to use Pygame Zero (TeCoEd)

Hardware

• Phidgets make a range of electronic devices - sensors, motors, input devices, and more - that connect to your computer over USB and can be used from Python programs. They have a range of Pygame Zero projects for you to try with Phidgets, and they offer a discount for educators.

Other libraries like Pygame Zero

Pygame Zero started a trend for Python “zero” libraries. Our friends have created these great libraries. Some of these can be combined with Pygame Zero!

Network Zero

Network Zero makes it simpler to have several machines or several processes on one machine discovering each other and talking across a network.

Caution

If you want to use Network Zero with Pygame Zero, make sure you don’t let it block (stop everything while waiting for messages). This will interrupt Pygame Zero so that it stops animating the screen or even responding to input. Always set the wait_for_s or wait_for_reply_s options to 0 seconds.

GUI Zero

GUI Zero is a library for creating Graphical User Interfaces (GUIs) with windows, buttons, sliders, textboxes and so on.

Because GUI Zero and Pygame Zero both provide different approaches for drawing to the screen, they are not usable together.

GPIO Zero

GPIO Zero is a library for controlling devices connected to the General Purpose Input/Output (GPIO) pins on a Raspberry Pi.

GPIO Zero generally runs in its own thread, meaning that it will usually work very well with Pygame Zero.

Caution

When copying GPIO Zero examples, do not copy the time.sleep() function calls or while True: loops, as these will stop Pygame Zero animating the screen or responding to input. Use Clock functions instead to call functions periodically, or the update() function to check a value every frame.

Adventurelib

Adventurelib is a library for creating making text-based games easier to write (and which doesn’t do everything for you!).

Writing text-based games requires a very different set of skills to writing graphical games. Adventurelib is pitched at a slightly more advanced level of Python programmer than Pygame Zero.

Adventurelib cannot currently be combined with Pygame Zero.

Blue Dot

Blue Dot allows you to control your Raspberry Pi projects wirelessly using an Android device as a Bluetooth remote.

Blue Dot generally runs in its own thread, meaning that it will usually work very well with Pygame Zero.

Caution

Avoid time.sleep() function calls, while True: loops and Blue Dot’s blocking wait_for_press and wait_for_release methods, as these will stop Pygame Zero animating the screen or responding to input. Use Clock functions instead to call functions periodically, or the update() function to check a value every frame.

Tip

Know of another library that belongs here?

Open an issue on the issue tracker to let us know!

Changelog

1.3 - unreleased

• New: Actors can be made transparent by assigning to actor.opacity (based on work by Rhys Puddephatt and charlesej)
• New: screen.fill() now takes gcolor, creating a vertical-linear gradient
• New: a REPL has been added, which allows exploring a game’s state while it is running.
• New: Added a storage API, which preserves data across game runs (based on work by Ian Salmons and Gustavo Ferreira)

1.2 - 2018-02-24

• New: Actors can be rotated by assigning to actor.angle
• New: Actors now have angle_to() and distance_to() methods.
• New: Actors are no longer subclasses of Rect, though they provide the same methods/properties. However they are now provided with floating point precision.
• New: tone.play() function to allow playing musical notes.
• New: pgzrun.go() to allow running Pygame Zero from an IDE (see Running Pygame Zero in IDLE and other IDEs).
• New: show joypad icon by default
• Examples: add Asteroids example game (thanks to Ian Salmons)
• Examples: add Flappy Bird example game
• Examples: add Tetra example game (thanks to David Bern)
• Docs: Add a logo, fonts and colours to the documentation.
• Docs: Documentation for the anchor point system for Actors
• Docs: Add Migrating from Scratch documentation
• Fix: on_mouse_move() did not correctly handle the buttons parameter.
• Fix: Error message when resource not found incorrectly named last extension searched.
• Fix: Drawing wrapped text would cause crashes.
• Fix: animate() now replaces animations of the same property, rather than creating two animations which fight.
• Updated ptext to a revision as of 2016-11-17.
• Removed: removed undocumented British English centrex, centrey, centre attribute aliases on ZRect (because they are not Rect-compatible).

1.1 - 2015-08-03

• Added a spell checker that will point out hook or parameter names that have been misspelled when the program starts.
• New ZRect built-in class, API compatible with Rect, but which accepts coordinates with floating point precision.
• Refactor of built-in keyboard object to fix attribute case consistency. This also allows querying key state by keys constants, eg. keyboard[keys.LEFT].
• Provide much better information when sound files are in an unsupported format.
• screen.blit() now accepts an image name string as well as a Surface object, for consistency with Actor.
• Fixed a bug with non-focusable windows and other event bugs when running in a virtualenv on Mac OS X.
• Actor can now be positioned by any of its border points (eg. topleft, midright) directly in the constructor.
• Added additional example games in the examples/ directory.

1.0.2 - 2015-06-04

• Fix: ensure compatibility with Python 3.2

1.0.1 - 2015-05-31

This is a bugfix release.

• Fix: Actor is now positioned to the top left of the window if pos is unspecified, rather than appearing partially off-screen.

• Fix: repeating clock events can now unschedule/reschedule themselves

  Previously a callback that tried to unschedule itself would have had no effect, because after the callback returns it was rescheduled by the clock.

  This applies also to schedule_unique.

• Fix: runner now correctly displays tracebacks from user code

• New: Eliminate redraws when nothing has changed

  Redraws will now happen only if:

  • The screen has not yet been drawn
  • You have defined an update() function
  • An input event has been fired
  • The clock has dispatched an event

1.0 - 2015-05-29

• New: Added anchor parameter to Actor, offering control over where its pos attribute refers to. By default it now refers to the center.

• New: Added Ctrl-Q/⌘-Q as a hard-coded keyboard shortcut to exit a game.

• New: on_mouse_* and on_key_* receive IntEnum values as button and key parameters, respectively. This simplifies debugging and enables usage like:

  if button is button.LEFT:
  

1.0beta1 - 2015-05-19

Initial public (preview) release.

Stickers by

Sticker Mule have graciously offered to provide Pygame Zero laptop stickers for learners.

Laptop Stickers

Sticker Mule have graciously offered to provide a number of stickers for Pygame Zero users for free.

Laptop stickers are a great way to encourage students to continue tinkering and learning, as well as spreading the word about Pygame Zero.

The stickers should look a little like this (not to scale):

For learners

Due to the costs of distribution, and because Pygame Zero is a free community library, we don’t have a way of getting stickers directly to you yet.

It may be possible to obtain stickers at conferences and meet-ups. Please check back soon.

For educators/meet-ups

We would like to distribute stickers primarily via educators and educational meet-ups. At this time it is not known how many stickers we will be able to distribute in this way (and it may be prohibitively expensive to ship them outside the UK).

Please fill out our Google Form to express your interest.

For developers

Free stickers are primarily intended for learners. However, if a pull request you make to Pygame Zero or a translation is accepted, we would be very happy to give you a free laptop sticker if the opportunity arises.

Please request a sticker in your Pull Request comments (or make yourself known at a conference/meet-up).

If you attend educational events or Python events regularly, and you would be willing to distribute stickers, this could also be useful. Please let us know.

Improving Pygame Zero

Roadmap

Pygame Zero is an open source project, and as with any such project, the development roadmap is subject to change.

This document just lays out some goals for future releases, but there is no guarantee that these targets will be hit.

Translations

Pygame Zero is aimed at young users, whose English skills might not be good enough to read the documentation if it isn’t in their own language.

Adding translations of the documentation would help to bring Pygame Zero to new users. This is something that needs contributors to help with. My own language skills aren’t good enough!

Please see the translating guide if you think you can help.

Gamepad Support

Github Issue: #70

SNES-style gamepads are now extremely cheap. For example, they are sold for a few pounds from the Pi Hut, in packs of 2 at Amazon, and even in some Raspberry Pi bundles.

Gamepad support should not be limited to these specific models; rather, we should treat this as a lowest-common-denominator across modern gamepads, as nearly all more modern gamepads have at least as many buttons and axes.

This feature needs to be added in a way that will not require a gamepad to play any Pygame Zero game, in order to follow the principle of Make it accessible.

Surface juggling

Github Issue: #71

Pygame experts make lots of use of off-screen surfaces to create interesting effects.

Pygame Zero chose to consider only the screen surface, which we wrap with a richer Screen API for drawing, etc.

The problem is that there is no easy path to using additional surfaces - Pygame Zero immediately becomes dead weight as you start to look past that curtain.

We should look to smooth out this path to make Pygame Zero Actors and Screen work better with custom surfaces.

Storage

Note

A storage API has now been developed and is planned for inclusion in Pygame Zero 1.3.

Github Issue: #33

It would be useful for users to be able to save and load data.

The obvious application is save games, but saving and loading whole games can be pretty hard to get right. The simpler application would just be saving settings, customisations, high scores, or the highest level reached.

Python of course has APIs for reading and writing files, but this has additional complexity that teachers might not want to teach immediately.

Principles of Pygame Zero

Please read the following carefully before contributing.

Because Pygame Zero is aimed at beginners we must take extra care to avoid introducting hurdles for programmers who have not yet learned to deal with them.

Make it accessible

The main aim of Pygame Zero is to be accessible to beginner programmers. The design of the API is, of course, influenced by this.

This also applies to things like hardware requirements: Pygame Zero chose originally to support only keyboard and mouse input, in order to be accessible to any user.

Be conservative

Early in the development of Pygame Zero, Richard and I (Daniel) went backwards and forwards over various features. We put them in, tried them and took them out again.

Features should be rejected if they are too experimental, or if they might cause confusion.

This also applies to things like OS support: we disallow filenames that are not likely to be compatible across operating systems.

Just Work

Pygame Zero wraps Pygame almost completely - but we don’t expose all the features. We expose only the features that work really well without extra fuss, and hide some of the other features that work less well or need extra steps.

Minimise runtime cost

At the end of the day, Pygame Zero is a games framework and performance is an issue.

Doing expensive checking every frame to catch a potential pitfall is not really acceptable. Instead, we might check at start up time, or check only when an exception is raised to diagnose it and report more information.

Error clearly

When exceptions are thrown by Pygame Zero, they should have clear error messages that explain the problem.

Document well

Like all projects, Pygame Zero needs good documentation. Pull requests are more likely to be accepted if they include the necessary documentation.

Try to avoid complicated sentences and technical terms in the documentation, so that it is more easily readable by inexperienced programmers.

Minimise breaking changes

In educational environments, users don’t always have control of the version of a library they use. They don’t know how to install or upgrade to the latest version.

It is more important to get the features right first time than in many other projects.

Contributing to Pygame Zero

The Pygame Zero project is hosted on GitHub:

https://github.com/lordmauve/pgzero

Reporting an bug or request

You can report bugs, or request features that you think should be in Pygame Zero, using the Github issue tracker.

Here are some things to bear in mind before you do this:

• It might not just be you! You should check if someone has already reported the issue by searching through the existing issues - both open and closed.
• The developers need to know what version of Pygame Zero you are using, and what operating system you are running (Windows, Mac, Linux etc) and version (Windows 10, Ubuntu 16.04, etc).

How to do a pull request

You can make changes to Pygame Zero by creating a pull request.

It’s a good idea to report an issue first, so that we can discuss whether your change makes sense.

Github has help on how to create a pull request, but here’s the quick version:

1. Make sure you are logged into Github.

2. Go to the Github page for Pygame Zero.

3. Click “Fork” to create your own fork of the repository.

4. Clone this fork to your own computer:

   git clone git@github.com:yourusername/pgzero.git
   

   Remember to change yourusername to your Github username.

5. Create a branch in which to do your changes. Pick a branch name that describes the change you want to make.

   git checkout -b my-new-branch master
   

6. Make the changes you want.

7. Add the files that you want to commit:

   git add pgzero
   

8. Commit the files with a clear commit message:

   git commit -m "Fixed issue #42 by renaming parameters"
   

   You can do steps 6 to 8 as many times as you want until you’re happy.

9. Push the commit back to your fork.

   git push --set-upstream origin my-new-branch
   

10. Go to the Github page for your fork, and click on the “Create pull request” button.

Development installation

It’s possible to create a locally-editable install using pip. From the root directory of the checked out source, run:

pip3 install --editable .

The installed version will now reflect any local changes you make.

Alternatively, if you don’t want to install it at all, it may be run with:

python3 -m pgzero <name of pgzero script>

For example:

python3 -m pgzero examples/basic/demo1.py

How to run tests

The tests can be run with

python3 setup.py test

Helping to translate the documentation

Pygame Zero’s APIs will always be English, but we can bring Pygame Zero to more users around the world if the documentation is available in their language.

If you are fluent in another language, please consider contributing by translating all or part of the documentation.

The documentation is written in reStructuredText, which is a text-based markup language for technical documentation. As much as possible, the existing formatting should be preserved. reStructuredText isn’t too difficult once you get used to it.

Creating a translation is done by creating a separate repository on Github with a copy of the documentation, rewritten (at least in part) into the language you would like to support. One advantage of this is that you can work on translations at your own pace, without having to submit pull requests back to the pgzero project itself. Please see the translation guide on Read The Docs for details.

If this sounds like something you could tackle, here’s how you might go about it:

1. First, open an issue on the pgzero issue tracker. You should search for an existing issue covering the translation you want to do, before opening a new one. This will help ensure that you don’t do translation work that has already been done by someone else (perhaps you can collaborate instead).
2. Create a new Github repository under your user, called pgzero-language, eg. pgzero-spanish if you’re going to translate into Spanish.
3. Clone the repository to your own computer.
4. Download the Pygame Zero doc/ directory and commit it in your project. You can do this by extracting them from repository ZIP file. You only need the doc/ directory from the ZIP file. You can delete the other files.
5. Now, work through the .rst files in the docs directory, translating, using your preferred editor. You should commit regularly, and push your commits to Github.
6. Post a link to your repository as a comment in the Github issue you created in step 1. You can do this as soon as you have some progress to show; this will help people collaborate with you on the translation if they are interested.
7. Set up the documentation to build on Read The Docs. Again, post a comment on the Github issue when you have this working.
8. We can then link up the new, translated documentation with the Pygame Zero documentation.

Note that Pygame Zero will have updates, and the documentation will be changed accordingly. Using Git it is possible to see a diff of what changed in the English documentation, so that you can make corresponding changes in the translated documentation.