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Pygame – Random Movement of Object

  • Difficulty Level : Expert
  • Last Updated : 24 Sep, 2021

Prerequisite: How to draw rectangle in Pygame?

In this article, we will learn how we can add random movements in objects using PyGame in Python.

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Random movement in a single object

To add random movement in our object we are going to use randint method of the random module.



Syntax: random.randint(a, b)

Parameters:

a and b : Two integers 

Returns: Return a random integer that lies between a and b.

First, a frame with necessary adjustments is created, then an object is placed on the window to depict movement. Now by using randint() and setting other relevant parameters we can change the position of the object randomly.

Example: Random movement in one object

Python3




# Importing the pygame module
import pygame
from pygame.locals import *
 
# Import randint method random module
from random import randint
 
# Initiate pygame and give permission
# to use pygame's functionality
pygame.init()
 
# Create a display surface object
# of specific dimension
window = pygame.display.set_mode((600, 600))
 
# Creating a new clock object to
# track the amount of time
clock = pygame.time.Clock()
 
# Creating a variable for direction
direction = 1
 
# Creating a new rect for player
player_rect = Rect(100, 100, 50, 50)
 
# Starting speed
speed_x = 5
speed_y = 4
 
# Creating a boolean variable that
# we will use to run the while loop
run = True
 
# Creating an infinite loop
# to run our game
while run:
 
    # Setting the framerate to 60fps
    clock.tick(60)
 
    # Changing the direction and x,y coordinate
    # of the object if the coordinate of left
    # side is less than equal to 20 or right side coordinate
    # is greater than equal to 580
    if player_rect.left <= 20 or player_rect.right >= 580:
        direction *= -1
        speed_x = randint(0, 8) * direction
        speed_y = randint(0, 8) * direction
 
        # Changing the value if speed_x
        # and speed_y both are zero
        if speed_x == 0 and speed_y == 0:
            speed_x = randint(2, 8) * direction
            speed_y = randint(2, 8) * direction
 
    # Changing the direction and x,y coordinate
    # of the object if the coordinate of top
    # side is less than equal to 20 or bottom side coordinate
    # is greater than equal to 580
    if player_rect.top <= 20 or player_rect.bottom >= 580:
        direction *= -1
        speed_x = randint(0, 8) * direction
        speed_y = randint(0, 8) * direction
 
        # Changing the value if speed_x
        # and speed_y both are zero
        if speed_x == 0 and speed_y == 0:
            speed_x = randint(2, 8) * direction
            speed_y = randint(2, 8) * direction
 
    # Adding speed_x and speed_y
    # in left and top coordinates of object
    player_rect.left += speed_x
    player_rect.top += speed_y
 
    # Drawing player rect
    pygame.draw.rect(window, (0,   255,   0), player_rect)
 
    # Updating the display surface
    pygame.display.update()
 
    # Filling the window with white color
    window.fill((255, 255, 255))

Output:



Random movement in more than one object

To add random movement in more than one object we are going to create separate speed and direction variables for the objects. Then we are going to check if the objects are colliding or not with the help of colliderect() method.

Syntax: pygame.Rect.colliderect(rect1 , rect2)

Parameters:

It will take two rects as its parameters.

Returns:

Returns true if any portion of either rectangle overlap.

Example: Random movement in two objects

Python3




# Importing the pygame module
import pygame
from pygame.locals import *
 
# Import randint method random module
from random import randint
 
# Initiate pygame and give permission
# to use pygame's functionality
pygame.init()
 
# Create a display surface object
# of specific dimension
window = pygame.display.set_mode((600, 600))
 
# Creating a new clock object to
# track the amount of time
clock = pygame.time.Clock()
 
# Creating a variable for direction
# of object 1
direction_a = 1
 
# Creating a variable for direction
# of object 2
direction_b = 1
 
# Creating a new rect for first object
player_rect = Rect(100, 100, 50, 50)
 
# Creating a new rect for second object
player_rect2 = Rect(200, 200, 50, 50)
 
# Starting speed for object 1
speed_x1 = 5
speed_y1 = 4
 
# Starting speed for object 2
speed_x2 = 5
speed_y2 = 4
 
# Creating a boolean variable that
# we will use to run the while loop
run = True
 
# Creating an infinite loop
# to run our game
while run:
 
    # Setting the framerate to 60fps
    clock.tick(60)
 
    # Changing the direction and x,y coordinate
    # of the object if the coordinate of left
    # side is less than equal to 20 or right side coordinate
    # is greater than equal to 580
    if player_rect.left <= 20 or player_rect.right >= 580:
        direction_a *= -1
        speed_x1 = randint(0, 8)
        speed_y1 = randint(0, 8)
 
        # Changing the value if speed_x
        # and speed_y both are zero
        if speed_x1 == 0 and speed_y1 == 0:
            speed_x1 = randint(2, 8)
            speed_y1 = randint(2, 8)
 
    # Changing the direction and x,y coordinate
    # of the object if the coordinate of top
    # side is less than equal to 20 or bottom side coordinate
    # is greater than equal to 580
    if player_rect.top <= 20 or player_rect.bottom >= 580:
        direction_a *= -1
        speed_x1 = randint(0, 8)
        speed_y1 = randint(0, 8)
 
        # Changing the value if speed_x
        # and speed_y both are zero
        if speed_x1 == 0 and speed_y1 == 0:
            speed_x1 = randint(2, 8)
            speed_y1 = randint(2, 8)
 
    # Changing the direction and x,y coordinate
    # of the object2 if the coordinate of left
    # side is less than equal to 20 or right side coordinate
    # is greater than equal to 580
    if player_rect2.left <= 20 or player_rect2.right >= 580:
        direction_b *= -1
        speed_x2 = randint(0, 8)
        speed_y2 = randint(0, 8)
 
        # Changing the value if speed_x
        # and speed_y both are zero
        if speed_x2 == 0 and speed_y2 == 0:
            speed_x2 = randint(2, 8)
            speed_y2 = randint(2, 8)
 
    # Changing the direction and x,y coordinate
    # of the object2 if the coordinate of top
    # side is less than equal to 20 or bottom side coordinate
    # is greater than equal to 580
    if player_rect2.top <= 20 or player_rect2.bottom >= 580:
        direction_b *= -1
        speed_x2 = randint(0, 8)
        speed_y2 = randint(0, 8)
 
        # Changing the value if speed_x
        # and speed_y both are zero
        if speed_x2 == 0 and speed_y2 == 0:
            speed_x2 = randint(2, 8)
            speed_y2 = randint(2, 8)
 
    # Adding speed_x1 and speed_y1
    # in left and top coordinates of object
    # ad multiplying with direction_a
    player_rect.left += speed_x1 * direction_a
    player_rect.top += speed_y1 * direction_a
 
    # Adding speed_x2 and speed_y2
    # in left and top coordinates of object2
    # and multiplying with direction_b
    player_rect2.left += speed_x2 * direction_b
    player_rect2.top += speed_y2 * direction_b
 
    # Checking if player is colliding
    # with platform or not using the
    # colliderect() method.
    # It will return a boolean value
    collide = pygame.Rect.colliderect(player_rect, player_rect2)
 
    # If the objects are colliding
    # then changing their direction
    if collide:
        direction_a *= -1
        direction_b *= -1
 
    # Drawing player rect
    pygame.draw.rect(window, (0,   255,   0), player_rect)
    # Drawing player rect2
    pygame.draw.rect(window, (0,   0,   255), player_rect2)
 
    # Updating the display surface
    pygame.display.update()
 
    # Filling the window with white color
    window.fill((255, 255, 255))

Output:




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