Code:

import pygame, os
from pygame.locals import*


def loadimage(name, transparent=0):
    fullname = os.path.join('data', name)
    image = pygame.image.load(fullname)
    if transparent:
        image.set_colorkey(image.get_at((0,0)))
    return image.convert(), image.get_rect()


class Cat(pygame.sprite.Sprite):
    def __init__(self):
        pygame.sprite.Sprite.__init__(self)
        self.image, self.rect = loadimage('macka.png',1)
        screen = pygame.display.get_surface()
        area = screen.get_rect()
        self.rect.bottomleft = 0,0
        self.acceleration = 0 
        self.inair = 1    #inair = Cat in air? True or Flase
        self.speed = 9
        self.direction = 0
    def update(self):
        if self.inair:
            self.acceleration +=1
        self.rect.move_ip(self.direction*self.speed, self.acceleration)
        collision = self.rect.collidelistall(florsrect)
        if collision != []:
            #Cheking collision with platforms
            for fi in collision: #fi is flor index
                if florsrect[fi].top < self.rect.bottom:
                    self.rect.bottom = florsrect[fi].top
                    self.inair = 0
                    self.accelearation = 0
        else:
            self.inair = 1
    
            
    def jump(self):
        if not self.inair:
            self.acceleration =-15
            self.inair = 1

class Flor(pygame.sprite.Sprite):
    def __init__(self, pos):
        pygame.sprite.Sprite.__init__(self)
        self.image = pygame.Surface((200,20))
        self.image.fill((0,0,0))
        
        self.rect = self.image.get_rect()
        self.rect.topleft = pos

def main():
    global florsrect
    pygame.init()
    screen = pygame.display.set_mode((640,480))
    #Objects
    clock = pygame.time.Clock()
    c = Cat()
    flors =[
        Flor((0,400)),
        Flor((100,330)),
        Flor((0,240))
            ]
    florsrect = []
    for x in flors:
        florsrect.append(x.rect)
    #Background
    background = pygame.Surface(screen.get_size()).convert()
    background.fill((100,125,0))
    screen.blit(background, (0,0))
    pygame.display.flip()
    #Sprites
    allsprites= [c]
    for x in flors:
        allsprites.append(x)
        
    #MAIN LOOP
    while 1:
        clock.tick(60)       
        #commands
        for event in pygame.event.get():
            if (event.type == KEYDOWN and event.key == K_ESCAPE):
                pygame.quit()
                return
        keystate = pygame.key.get_pressed()
        c.direction = keystate[K_RIGHT] - keystate[K_LEFT]
        if keystate[K_UP]:c.jump()

        #draw everything
        screen.blit(background, (0,0))
        for sprite in allsprites:
            sprite.update()
            screen.blit(sprite.image,sprite.rect)
        pygame.display.flip()
    
            
main()