- Example: Adding and Deleting Shapes
from cmu_112_graphics import *
def appStarted(app):
app.circleCenters = [ ]
def mousePressed(app, event):
newCircleCenter = (event.x, event.y)
app.circleCenters.append(newCircleCenter)
def keyPressed(app, event):
if (event.key == 'd'):
if (len(app.circleCenters) > 0):
app.circleCenters.pop(0)
else:
print('No more circles to delete!')
def redrawAll(app, canvas):
# draw the circles
for circleCenter in app.circleCenters:
(cx, cy) = circleCenter
r = 20
canvas.create_oval(cx-r, cy-r, cx+r, cy+r, fill='cyan')
# draw the text
canvas.create_text(app.width/2, 20,
text='Example: Adding and Deleting Shapes', fill='black')
canvas.create_text(app.width/2, 40,
text='Mouse clicks create circles', fill='black')
canvas.create_text(app.width/2, 60,
text='Pressing "d" deletes circles', fill='black')
runApp(width=400, height=400)
- Example: Snake
Here is a 4-part video explaining how to write this version of Snake:
- Draw the board and the Snake
- Add motion and gameOver
- Add food and self-collision
- Add the timer and finish the game
from cmu_112_graphics import *
import random
def appStarted(app):
app.rows = 10
app.cols = 10
app.margin = 5 # margin around grid
app.timerDelay = 250
initSnakeAndFood(app)
app.waitingForFirstKeyPress = True
def initSnakeAndFood(app):
app.snake = [(0,0)]
app.direction = (0, +1) # (drow, dcol)
placeFood(app)
app.gameOver = False
# getCellBounds from grid-demo.py
def getCellBounds(app, row, col):
# aka 'modelToView'
# returns (x0, y0, x1, y1) corners/bounding box of given cell in grid
gridWidth = app.width - 2*app.margin
gridHeight = app.height - 2*app.margin
x0 = app.margin + gridWidth * col / app.cols
x1 = app.margin + gridWidth * (col+1) / app.cols
y0 = app.margin + gridHeight * row / app.rows
y1 = app.margin + gridHeight * (row+1) / app.rows
return (x0, y0, x1, y1)
def keyPressed(app, event):
if (app.waitingForFirstKeyPress):
app.waitingForFirstKeyPress = False
elif (event.key == 'r'):
initSnakeAndFood(app)
elif app.gameOver:
return
elif (event.key == 'Up'): app.direction = (-1, 0)
elif (event.key == 'Down'): app.direction = (+1, 0)
elif (event.key == 'Left'): app.direction = (0, -1)
elif (event.key == 'Right'): app.direction = (0, +1)
# elif (event.key == 's'):
# this was only here for debugging, before we turned on the timer
# takeStep(app)
def timerFired(app):
if app.gameOver or app.waitingForFirstKeyPress: return
takeStep(app)
def takeStep(app):
(drow, dcol) = app.direction
(headRow, headCol) = app.snake[0]
(newRow, newCol) = (headRow+drow, headCol+dcol)
if ((newRow < 0) or (newRow >= app.rows) or
(newCol < 0) or (newCol >= app.cols) or
((newRow, newCol) in app.snake)):
app.gameOver = True
else:
app.snake.insert(0, (newRow, newCol))
if (app.foodPosition == (newRow, newCol)):
placeFood(app)
else:
# didn't eat, so remove old tail (slither forward)
app.snake.pop()
def placeFood(app):
# Keep trying random positions until we find one that is not in
# the snake. Note: there are more sophisticated ways to do this.
while True:
row = random.randint(0, app.rows-1)
col = random.randint(0, app.cols-1)
if (row,col) not in app.snake:
app.foodPosition = (row, col)
return
def drawBoard(app, canvas):
for row in range(app.rows):
for col in range(app.cols):
(x0, y0, x1, y1) = getCellBounds(app, row, col)
canvas.create_rectangle(x0, y0, x1, y1,
fill='white', outline='black')
def drawSnake(app, canvas):
for (row, col) in app.snake:
(x0, y0, x1, y1) = getCellBounds(app, row, col)
canvas.create_oval(x0, y0, x1, y1, fill='blue')
def drawFood(app, canvas):
if (app.foodPosition != None):
(row, col) = app.foodPosition
(x0, y0, x1, y1) = getCellBounds(app, row, col)
canvas.create_oval(x0, y0, x1, y1, fill='green')
def drawGameOver(app, canvas):
if (app.gameOver):
canvas.create_text(app.width/2, app.height/2, text='Game over!',
font='Arial 26 bold', fill='black')
canvas.create_text(app.width/2, app.height/2+40,
text='Press r to restart!',
font='Arial 26 bold', fill='black')
def redrawAll(app, canvas):
if (app.waitingForFirstKeyPress):
canvas.create_text(app.width/2, app.height/2,
text='Press any key to start!',
font='Arial 26 bold', fill='black')
else:
drawBoard(app, canvas)
drawSnake(app, canvas)
drawFood(app, canvas)
drawGameOver(app, canvas)
runApp(width=400, height=400)
- Snake and MVC
| Model |
View |
Controller |
| app.rows |
redrawAll() |
keyPressed() |
| app.cols |
drawGameOver() |
timerFired() |
| app.margin |
drawFood() |
takeStep() |
| app.waitingForFirstKeyPress |
drawSnake() |
placeFood() |
| app.snake |
drawBoard() |
appStarted() |
| app.direction |
|
|
| app.foodPosition |
|
|
| + all game state |
+ all drawing functions |
+ all event-triggered actions |