Jump and run in 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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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 > 0:
                F = ( 0.5 * self.m * (self.v*self.v) )
                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 >= 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):
        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):
    def on_render(self):
    def on_cleanup(self):
    def on_execute(self):
        if self.on_init() == False:
            self._running = False
        while( self._running ):
            keys = pygame.key.get_pressed() 
            if (keys[K_RIGHT]):
            if (keys[K_LEFT]):
            if (keys[K_UP]):
            if (keys[K_ESCAPE]):
                self._running = False
if __name__ == "__main__" :
    theApp = App()

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.


3 thoughts on “Jump and run in Pygame

  1. John - August 9, 2015

    Very helpful tutorial for understanding pygame programming.

    Your physics is a little off. Force, F = ma. The expression 1/2 * m * v^2 is kinetic energy not force. But what you really want to do is calculate the change in the vertical y-coordinate for constant gravity acceleration while jumping. The change in y-coordinate is given by dy = v * dt, where dt is the constant time step. The vertical velocity, v, does decrease linearly due to constant acceleration (because v = at) as your example program does. But the F term should be proportional to v not v^2. If you change (self.v*self.v) to (self.v) you don’t need the if/else because the expression proportional to self.v changes sign with self.v. Mass doesn’t play into vertical velocity (ignoring air drag) as all objects are accelerated by gravity at the same rate.

    To keep changes to a minimum, I replaced the “if self.v>0” expression for F with one line:
    F = ( self.m * self.v)
    Then I changed self.m = 8 to make jump height about same as original.

    Changing the code that handles the jump physics results in a nice parabolic jump as in real world physics. The velocity squared physics rises quickly initially and hovers at the top of the arc longer. That may be desirable for some games, but it isn’t how jumping works in the real world.

    1. Staff - August 10, 2015

      Thanks John! I will update the code when I finished the to-do list

  2. Thor - May 29, 2015

    Thanks, this is a rock-solid foundation to start with 🙂

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