Category: games

pygame

In this article you will learn how to implement jump and run logic in Pygame. To do so, we will implement the player logic.

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Movement
Moving left and right is similar to the previous tutorial and simply mean changing the (x,y) position of the player. For jumping, we use a formula from classical mechanics:

F = 1/2 * m * v^2

Where F is the force up/down, m is the mass of your object and v is the velocity. The velocity goes down over time because when the player jumps the velocity will not increase more in this simulation. If the player reaches the ground, the jump ends. In Python, we set a variable isjump to indicate if the player is jumping or not. If the player is, its position will be updated according to the above formula.

Full Code:

from pygame.locals import *
import pygame
import math
from time import sleep
 
class Player:
    x = 10
    y = 500
    speed = 10

    # Stores if player is jumping or not.
    isjump = 0     
    
    # Force (v) up and mass m.
    v = 8 
    m = 2
            
    def moveRight(self):
        self.x = self.x + self.speed
 
    def moveLeft(self):
        self.x = self.x - self.speed
 
    def jump(self):
        self.isjump = 1

    def update(self):
        if self.isjump:
            # Calculate force (F). F = 0.5 * mass * velocity^2.
            if self.v &gt; 0:
                F = ( 0.5 * self.m * (self.v*self.v) )
            else:
                F = -( 0.5 * self.m * (self.v*self.v) )
    
            # Change position
            self.y = self.y - F

            # Change velocity
            self.v = self.v - 1

            # If ground is reached, reset variables.
            if self.y &gt;= 500:
                self.y = 500
                self.isjump = 0
                self.v = 8              
          

class App:
 
    windowWidth = 800
    windowHeight = 600
    player = 0
 
    def __init__(self):
        self._running = True
        self._display_surf = None
        self._image_surf = None
        self.player = Player() 
 
    def on_init(self):
        pygame.init()
        self._display_surf = pygame.display.set_mode((self.windowWidth,self.windowHeight), pygame.HWSURFACE)
        
        pygame.display.set_caption('Pygame pythonspot.com example')
        self._running = True
        self._image_surf = pygame.image.load("pygame.png").convert()
 
    def on_event(self, event):
        if event.type == QUIT:
            self._running = False
 
    def on_loop(self):
        pass
    
    def on_render(self):
        self._display_surf.fill((0,0,0))
        self._display_surf.blit(self._image_surf,(self.player.x,self.player.y))
        self.player.update()
        pygame.display.flip()
        sleep(0.03)
 
    def on_cleanup(self):
        pygame.quit()
 
    def on_execute(self):
        if self.on_init() == False:
            self._running = False
 
        while( self._running ):
            pygame.event.pump()
            keys = pygame.key.get_pressed() 
            
            if (keys[K_RIGHT]):
                self.player.moveRight()
 
            if (keys[K_LEFT]):
                self.player.moveLeft()
 
            if (keys[K_UP]):
                self.player.jump()
 
            if (keys[K_ESCAPE]):
                self._running = False
 
            self.on_loop()
            self.on_render()
        self.on_cleanup()
 
if __name__ == "__main__" :
    theApp = App()
    theApp.on_execute()

If you want to jump on objects, simply add them to the screen, do collision detection and reset the jump variables if collision is true.

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python text game

In this article we will demonstrate how to create a simple guessing game.
The goal of the game is to guess the right number.

Example
An example run below:

Simple text game with Python

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Random number

The user will be asked to guess the random number. We first pick the random number:

from random import randint

x = randint(1,9)

The randint() function will pick a pseudo random number between 1 and 10. Then we have to continue until the correct number is found:

guess = -1

print("Guess the number below 10:")
while guess != x:
    guess = int(raw_input("Guess: "))

    if guess != x:
        print("Wrong guess")
    else:
        print("Guessed correctly")

Python Guessing Game

The code below starts the game:

from random import randint

x = randint(1,9)
guess = -1

print "Guess the number below 10:"
while guess != x:
    guess = int(raw_input("Guess: "))

    if guess != x:
        print("Wrong guess")
    else:
        print("Guessed correctly")

An example run:

Guess the number below 10:
Guess: 3
Wrong guess
Guess: 6
Wrong guess
..

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snake ai

In this article we will show you how to create basic game AI (Artificial Intelligence). This article will describe an AI for the game snake.

In this game (snake) both the computer and you play a snake, and the computer snake tries to catch you. In short: the opponent AI tries to determine and go to the destination point based on your location on the board.

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Adding the computer player:
We extend the code with a new class called Computer which will be our computer player. This contains routines to draw and move the computer snake.

class Computer:
    x = [0]
    y = [0]
    step = 44
    direction = 0
    length = 3
 
    updateCountMax = 2
    updateCount = 0

    def __init__(self, length):
       self.length = length
       for i in range(0,2000):
           self.x.append(-100)
           self.y.append(-100)

       # initial positions, no collision.
       self.x[0] = 1*44
       self.y[0] = 4*44

    def update(self):

        self.updateCount = self.updateCount + 1
        if self.updateCount &gt; self.updateCountMax:

            # update previous positions
            for i in range(self.length-1,0,-1):
                self.x[i] = self.x[i-1]
                self.y[i] = self.y[i-1]

            # update position of head of snake
            if self.direction == 0:
                self.x[0] = self.x[0] + self.step
            if self.direction == 1:
                self.x[0] = self.x[0] - self.step
            if self.direction == 2:
                self.y[0] = self.y[0] - self.step
            if self.direction == 3:
                self.y[0] = self.y[0] + self.step

            self.updateCount = 0


    def moveRight(self):
        self.direction = 0

    def moveLeft(self):
        self.direction = 1

    def moveUp(self):
        self.direction = 2

    def moveDown(self):
        self.direction = 3 

    def draw(self, surface, image):
        for i in range(0,self.length):
            surface.blit(image,(self.x[i],self.y[i]))

We then call the update and drawing method of the computer.

    def on_loop(self):
        self.player.update()
        self.computer.update()

....
    
    def on_render(self):
        self._display_surf.fill((0,0,0))
        self.player.draw(self._display_surf, self._image_surf)
        self.apple.draw(self._display_surf, self._apple_surf)
        self.computer.draw(self._display_surf, self._image_surf)
        pygame.display.flip()

This will make the computer snake move and be drawn on the screen. It has the same properties as the human player.

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Adding the intelligence to the computer player
Because this is a simple game, we do not need to create a complete thinking machine inside the game. We simply need some basic intelligence exhibited by our computer player. Intelligence in games is often quite limited because most of the time more complexity is not neccesary or there simply is not the time available to implement clever algorithms.

The algorithm we will add will simply go to the destination. It will neglect any obstacles (the human player).

def target(self,dx,dy):
    if self.x[0] &gt; dx:
        self.moveLeft()

    if self.x[0] &lt; dx:
        self.moveRight()

    if self.x[0] == dx:
        if self.y[0] &lt; dy:
            self.moveDown()

        if self.y[0] &gt; dy:
            self.moveUp()

Complete code
We end up with this complete code:

from pygame.locals import *
from random import randint
import pygame
import time

class Apple:
    x = 0
    y = 0
    step = 44

    def __init__(self,x,y):
        self.x = x * self.step
        self.y = y * self.step

    def draw(self, surface, image):
        surface.blit(image,(self.x, self.y)) 


class Player:
    x = [0]
    y = [0]
    step = 44
    direction = 0
    length = 3
 
    updateCountMax = 2
    updateCount = 0

    def __init__(self, length):
       self.length = length
       for i in range(0,2000):
           self.x.append(-100)
           self.y.append(-100)

       # initial positions, no collision.
       self.x[0] = 1*44
       self.x[0] = 2*44

    def update(self):

        self.updateCount = self.updateCount + 1
        if self.updateCount &gt; self.updateCountMax:

            # update previous positions
            for i in range(self.length-1,0,-1):
                self.x[i] = self.x[i-1]
                self.y[i] = self.y[i-1]

            # update position of head of snake
            if self.direction == 0:
                self.x[0] = self.x[0] + self.step
            if self.direction == 1:
                self.x[0] = self.x[0] - self.step
            if self.direction == 2:
                self.y[0] = self.y[0] - self.step
            if self.direction == 3:
                self.y[0] = self.y[0] + self.step

            self.updateCount = 0


    def moveRight(self):
        self.direction = 0

    def moveLeft(self):
        self.direction = 1

    def moveUp(self):
        self.direction = 2

    def moveDown(self):
        self.direction = 3 

    def draw(self, surface, image):
        for i in range(0,self.length):
            surface.blit(image,(self.x[i],self.y[i])) 



class Computer:
    x = [0]
    y = [0]
    step = 44
    direction = 0
    length = 3
 
    updateCountMax = 2
    updateCount = 0

    def __init__(self, length):
       self.length = length
       for i in range(0,2000):
           self.x.append(-100)
           self.y.append(-100)

       # initial positions, no collision.
       self.x[0] = 1*44
       self.y[0] = 4*44

    def update(self):

        self.updateCount = self.updateCount + 1
        if self.updateCount &gt; self.updateCountMax:

            # update previous positions
            for i in range(self.length-1,0,-1):
                self.x[i] = self.x[i-1]
                self.y[i] = self.y[i-1]

            # update position of head of snake
            if self.direction == 0:
                self.x[0] = self.x[0] + self.step
            if self.direction == 1:
                self.x[0] = self.x[0] - self.step
            if self.direction == 2:
                self.y[0] = self.y[0] - self.step
            if self.direction == 3:
                self.y[0] = self.y[0] + self.step

            self.updateCount = 0


    def moveRight(self):
        self.direction = 0

    def moveLeft(self):
        self.direction = 1

    def moveUp(self):
        self.direction = 2

    def moveDown(self):
        self.direction = 3 

    
    def target(self,dx,dy):
        if self.x[0] &gt; dx:
            self.moveLeft()

        if self.x[0] &lt; dx:
            self.moveRight()

        if self.x[0] == dx:
            if self.y[0] &lt; dy:
                self.moveDown()

            if self.y[0] &gt; dy:
                self.moveUp()

    def draw(self, surface, image):
        for i in range(0,self.length):
            surface.blit(image,(self.x[i],self.y[i])) 


class Game:
    def isCollision(self,x1,y1,x2,y2,bsize):
        if x1 &gt;= x2 and x1 &lt;= x2 + bsize:
            if y1 &gt;= y2 and y1 &lt;= y2 + bsize:
                return True
        return False

class App:

    windowWidth = 800
    windowHeight = 600
    player = 0
    apple = 0

    def __init__(self):
        self._running = True
        self._display_surf = None
        self._image_surf = None
        self._apple_surf = None
        self.game = Game()
        self.player = Player(5) 
        self.apple = Apple(8,5)
        self.computer = Computer(5)

    def on_init(self):
        pygame.init()
        self._display_surf = pygame.display.set_mode((self.windowWidth,self.windowHeight), pygame.HWSURFACE)
        
        pygame.display.set_caption('Pygame pythonspot.com example')
        self._running = True
        self._image_surf = pygame.image.load("pygame.png").convert()
        self._apple_surf = pygame.image.load("apple.png").convert()

    def on_event(self, event):
        if event.type == QUIT:
            self._running = False

    def on_loop(self):
        self.computer.target(self.apple.x, self.apple.y)
        self.player.update()
        self.computer.update()
        
        # does snake eat apple?
        for i in range(0,self.player.length):
            if self.game.isCollision(self.apple.x,self.apple.y,self.player.x[i], self.player.y[i],44):
                self.apple.x = randint(2,9) * 44
                self.apple.y = randint(2,9) * 44
                self.player.length = self.player.length + 1

        # does computer eat apple?
        for i in range(0,self.player.length):
            if self.game.isCollision(self.apple.x,self.apple.y,self.computer.x[i], self.computer.y[i],44):
                self.apple.x = randint(2,9) * 44
                self.apple.y = randint(2,9) * 44
                #self.computer.length = self.computer.length + 1


        # does snake collide with itself?
        for i in range(2,self.player.length):
            if self.game.isCollision(self.player.x[0],self.player.y[0],self.player.x[i], self.player.y[i],40):
                print "You lose! Collision: "
                print "x[0] (" + str(self.player.x[0]) + "," + str(self.player.y[0]) + ")"  
                print "x[" + str(i) + "] (" + str(self.player.x[i]) + "," + str(self.player.y[i]) + ")"  
                exit(0)
       
        pass
    
    def on_render(self):
        self._display_surf.fill((0,0,0))
        self.player.draw(self._display_surf, self._image_surf)
        self.apple.draw(self._display_surf, self._apple_surf)
        self.computer.draw(self._display_surf, self._image_surf)
        pygame.display.flip()
 
    def on_cleanup(self):
        pygame.quit()
 
    def on_execute(self):
        if self.on_init() == False:
            self._running = False
 
        while( self._running ):
            pygame.event.pump()
            keys = pygame.key.get_pressed() 
            
            if (keys[K_RIGHT]):
                self.player.moveRight()

            if (keys[K_LEFT]):
                self.player.moveLeft()

            if (keys[K_UP]):
                self.player.moveUp()

            if (keys[K_DOWN]):
                self.player.moveDown()

            if (keys[K_ESCAPE]):
                self._running = False

            self.on_loop()
            self.on_render()

            time.sleep (50.0 / 1000.0);
        self.on_cleanup()
 
if __name__ == "__main__" :
    theApp = App()
    theApp.on_execute()

python snake

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Conclusion
You learned how to create a basic computer player using an very simple AI algorithm.

Next: Learn basic sidescroller logic

Category: games

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