Why is jumping not working not working in pygame

Question

I can't figure out why my player is not jumping. I have defined jump and update functions as follows:

def jump(self):
     if self.is_jumping == False:
         self.is_jumping = True

def update(self):
    if self.is_jumping:
         self.y -= self.force

Here's the initialization

class Myman:
    def __init__(self, x, y, side):
        self.x  = x
        self.y = y
        self.side = side
        self.speed = 2
        self.is_jumping = False

I have implemented this in the main loop as follows:

while True:
    for event in pygame.event.get():
        if event.type == pygame.KEYDOWN:
            if event.key == pygame.K_SPACE:
                mm.jump()

    d.fill((98, 98, 98))
    mm.draw()
    mm.g()
    mm.update()


    if mm.y + mm.side > 550:
         mm.y = 550 - mm.side
         mm.falling = False

However, when I try to jump, it doesn't work. All the examples I have seen on jumping so far have done the same thing, but mine isn't working and I can't figure out why. Thanks for helping.

Here's the code for anyone who would like to check for reference.

import pygame, os

os.environ["SDL_VIDEO_CENTERED"] = "1"
pygame.init()

win = pygame.display
d = win.set_mode((1200, 600))
win.set_caption("Jump")

gravity = 0.1

class Myman:
    def __init__(self, x, y, side):
        self.x  = x
        self.y = y
        self.side = side
        self.speed = 2
        self.is_jumping = False
        self.force = 2

    def draw(self):
        pygame.draw.rect(d, (0 ,255, 0), (self.x, self.y, self.side, self.side))

    def g(self):
        global gravity
        self.y += gravity
        gravity += 0.01

    def move_left(self):
        self.x -= self.speed

    def move_right(self):
        self.x += self.speed

    def jump(self):
        if self.is_jumping == False:
            self.is_jumping = True

    def update(self):
        if self.is_jumping:
            self.y -= self.force


mm = Myman(600, 400, 20)

def platform():
    pygame.draw.rect(d, (0 ,0, 0), (0, 550, 1200, 50))

while True:
    for event in pygame.event.get():
        if event.type == pygame.KEYDOWN:
            if event.key == pygame.K_SPACE:
                mm.jump()

    d.fill((98, 98, 98))
    mm.draw()
    mm.g()
    mm.update()
    platform()
    keys = pygame.key.get_pressed()

    if keys[pygame.K_RIGHT]:
        mm.move_right()
    if keys[pygame.K_LEFT]:
        mm.move_left()

    if mm.y + mm.side >= 550:
        mm.y = 550 - mm.side
        mm.falling = False

    win.flip()

Kingsley · Accepted Answer

The problem is that your gravity is ever-increasing:

def g(self):
    global gravity
    self.y  += gravity
    gravity += 0.01        # <-- HERE

After just one second, gravity is 60 pixels per frame. This immediately more-than reverses any minor velocity change introduced by jumping.

So unless you want to do a real-time "physics" gravity model (which would be good), maybe just change the player's gravity for the millisecond duration of the jump. Give it negative gravity for the first half of the jump, then at the highest-point of the jump, the gravity reverts to normal. This is easily done based on a jump time.

Something like:

class Myman:
    JUMP_TIME = 1500  # milliseconds to jump apogee
    def __init__(self, x, y, side):
        self.x = x
        self.y = y
        self.jump_at = 0         # time of jump start
        # ... rest of code omitted

    def isJumping( self ):
       jumping = False
       time_now = pygame.time.get_ticks()
       if ( time_now - self.jump_at < 2 * Myman.JUMP_TIME ): # up and down time
           jumping = True
       return jumping

    def jump( self ):
        if ( not self.isJumping() ):   # is the player ready to jump again
            self.jump_at = pygame.time.get_ticks()  # time now

   def update( self ):
       if ( self.isJumping() ):
           time_now = pygame.time.get_ticks()
           # is the player going up, or coming down?
           if ( time_now - self.jump_at < Myman.JUMP_TIME ):
               self.gravity = -0.1                       # still jumping up
           else:
               self.gravity = 0.1                        # now going down
       # ... rest of code omitted

Style Note: I purposefully put brackets around all if expressions because I truly believe it makes the code more readable. This is in opposition to recommendations in PEP8.

Why is jumping not working not working in pygame

Answers (2)

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