Pygame Physics

#pygame Test by KNovak
import pygame, sys, os, math
from pygame.locals import *
pygame.init()
pygame.key.set_repeat(1)
fullscreen = False;

#startup settings
for arg in sys.argv:
    if arg == "-f":
        fullscreen = True


#Video Display information
vidinfo = pygame.display.Info()

if fullscreen == True:
    vidsize = (vidinfo.current_w, vidinfo.current_h)
    window = pygame.display.set_mode(vidsize, pygame.FULLSCREEN)
else:
    vidsize = (640,480)
    window = pygame.display.set_mode(vidsize)
pygame.display.set_caption('KNova Test Window')
screen = pygame.display.get_surface()
background = pygame.Surface((screen.get_width(), screen.get_height()))

#colors
WHITE = (255,255,255)
BLUE = (0,0,150)
GREEN = (0,150,0)

#text
def drawText (text, color, xloc, yloc, size):
    fontObj = pygame.font.Font('freesansbold.ttf', size)
    textSurface = fontObj.render(text, True, color)
    textRectObj = textSurface.get_rect()
    textRectObj.center = (xloc, yloc)
    return textSurface, textRectObj

#Sprite Class for the Ship Image
class Ship(pygame.sprite.Sprite):
    image = pygame.image.load("./resources/ship.png")
    image = image.convert()

    #initialization function
    def __init__(self, position=(100,100)):
        pygame.sprite.Sprite.__init__(self,self.groups)
        self.pos = position
        self.orig_image = Ship.image
        self.image = self.orig_image
        self.rect = self.image.get_rect()
        self.rect.center = self.pos
        self.angle = 0
        self.moveangle = 0
        self.vx = 0
        self.vy = 0
        self.maxvel = 3

    #move function
    def move(self, newpos):
        oldx, oldy = self.pos
        dx, dy = newpos
        self.pos = (oldx - dx, oldy - dy)
        self.rect.center = self.pos


    #update function which will replace both move and rotate
    def update(self):

        #handle rotations
        if self.angle >= 360:
            self.angle = 0
        if self.angle <= -360:
            self.angle = 0
        loc = self.rect.center
        self.image = pygame.transform.rotate(self.orig_image, self.angle)
        self.rect = self.image.get_rect()
        self.rect.center = loc

        #handle 2D movement
        self.move(getDirection(self.angle, self.vx, self.vy))

        #boundaries
        if self.pos[0] > vidsize[0]:
            #right
            self.vx = -self.vx
        if self.pos[0] < 0:
            #left
            self.vx = -self.vx
        if self.pos[1] > vidsize[1]:
            #bottom
            self.vy = -self.vy
        if self.pos[1] < 0:
            #top
            self.vy = -self.vy


spriteGroup = pygame.sprite.Group()
Ship.groups = spriteGroup
newShip = Ship()

#sprite group update
def spriteUpdate(group, screen, background):
    group.clear(screen, background)
    group.update()
    group.draw(screen)

#trig functions for updating position
def getDirection(angle,velx, vely):
    x = math.sin(math.radians(angle)) * velx
    y = math.cos(math.radians(angle)) * vely
    return (x,y)


#get keyboard events
def pyin(events):
    for event in events:
        if event.type == QUIT:
            sys.exit(0)
        if event.type == KEYDOWN:
            key = pygame.key.get_pressed()
            if (key[pygame.K_ESCAPE]):
                sys.exit(0)
            if (key[K_UP]):
                newShip.vx += 0.5
                newShip.vy += 0.5
                if newShip.vx >= newShip.maxvel: newShip.vx = newShip.maxvel
                if newShip.vy >= newShip.maxvel: newShip.vy = newShip.maxvel

            if (key[K_DOWN]):
                newShip.vx += -0.5
                newShip.vy += -0.5
                if newShip.vx <= (0-newShip.maxvel): newShip.vx = (0-newShip.maxvel)
                if newShip.vy <= (0-newShip.maxvel): newShip.vy = (0-newShip.maxvel)

            if (key[K_LEFT]):
                newShip.angle += 4
            if (key[K_RIGHT]):
                newShip.angle -= 4


while True:
    pyin(pygame.event.get())
#   pykey(pygame.key.get_pressed())
    pygame.display.update()
    spriteUpdate(spriteGroup, screen, background)