This is my entire sprites file.

import pygame as pg
from settings import *
vec = pg.math.Vector2

class Player(pg.sprite.Sprite):
    #sprite for the PLAYER
    def __init__(self):
        pg.sprite.Sprite.__init__(self)
        self.image = pg.Surface((30,40))
        self.image.fill(YELLOW)
        self.rect = self.image.get_rect()
        self.rect.center = (WIDTH / 2, HEIGHT - 30)
        self.pos = vec(WIDTH / 2, HEIGHT / 2)
        self.vel = vec(0,0)
        self.acc = vec(0,0)

    def jump(self):
        # jump only if standing on platform
        self.vel.y = -10


    def update(self):
        self.acc = vec(0, 0.5)
        keys = pg.key.get_pressed()
        if keys[pg.K_LEFT]:
            self.acc.x = -PLAYER_ACC
        if keys[pg.K_RIGHT]:
            self.acc.x = PLAYER_ACC

        # apply friction
        self.acc.x += self.vel.x * PLAYER_FRICTION


        # equations of motion
        self.vel += self.acc
        self.pos += self.vel + 0.5 * self.acc
        # wrap around the sides of the screen
        if self.pos.x > WIDTH:
            self.pos.x = 0
        if self.pos.x < 0:
            self.pos.x = WIDTH


        self.rect.midbottom = self.pos

class Platform(pg.sprite.Sprite):
    def __init__(self, x, y, w, h):
        pg.sprite.Sprite.__init__(self)
        self.image = pg.Surface((w, h))
        self.image.fill(GREEN)
        self.rect = self.image.get_rect()
        self.rect.x = x
        self.rect.y = y