pyopengl problems?

from OpenGL.GL import *
from OpenGL.GLUT import *

def _make_shader(stype, src):
    shader = glCreateShader(stype)
    glShaderSource(shader, src)
    glCompileShader(shader)

    if not glGetShaderiv(shader, GL_COMPILE_STATUS):
        err = glGetShaderInfoLog(shader)
        glDeleteShader(shader)
        raise Exception(err)
    return shader

verts = (GLfloat*8)()
for i, v in enumerate([-1.0, -1.0, 1.0, -1.0, -1.0,  1.0, 1.0,  1.0]):
    verts[i] = v
polys = (GLushort*6)()
for i, v in enumerate([0,1,3,1,2,3]):
    polys[i] = v

def init_gl():
    global program, posidx, vbuf, ebuf

    glEnable(GL_BLEND)
    glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA)
    glClearColor(0.5,0.5,0.5,1)
    glClearDepth(1.0)
    glDepthFunc(GL_LESS)
    glEnable(GL_DEPTH_TEST)
    glEnable(GL_TEXTURE_2D)
    glViewport(0,0,800,600)

    ######################################
    # Make the shaders and programs
    ######################################
    vshade = _make_shader(GL_VERTEX_SHADER, open("stupid.v.glsl").read())
    fshade = _make_shader(GL_FRAGMENT_SHADER, open("stupid.f.glsl").read())

    program = glCreateProgram()
    glAttachShader(program, vshade)
    glAttachShader(program, fshade)
    glLinkProgram(program)

    #######################################
    # Fetch positions, push poly to card
    #######################################
    posidx = glGetAttribLocation(program, "position")

    vbuf = glGenBuffers(1)
    ebuf = glGenBuffers(1)
    glBindBuffer(GL_ARRAY_BUFFER, vbuf)
    glBufferData(GL_ARRAY_BUFFER, verts, GL_STATIC_DRAW)
    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, ebuf)
    glBufferData(GL_ELEMENT_ARRAY_BUFFER, polys, GL_STATIC_DRAW)


#####################################
# Enter main drawing loop!
#####################################
def render():
    global program, posidx, vbuf, ebuf
    # Clear the screen
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT)
    glUseProgram(program)

    # Enable the position attribute
    glEnableVertexAttribArray(posidx)
    glBindBuffer(GL_ARRAY_BUFFER, vbuf)
    glVertexAttribPointer( posidx, 2, GL_FLOAT, GL_FALSE, 4*2, 0)

    # Draw the two triangles
    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, ebuf);
    glDrawElements(
        GL_TRIANGLES,           # mode
        6,           # count
        GL_UNSIGNED_SHORT,      # type
        0                       # element array buffer offset
    )

    glDisableVertexAttribArray(posidx)
    glutSwapBuffers()

def main():
    glutInit()
    glutInitDisplayMode(GLUT_RGB | GLUT_DEPTH | GLUT_DOUBLE);
    glutInitWindowSize(800, 600);
    glutCreateWindow("Flag");
    glutDisplayFunc(render);

    init_gl();

    glutMainLoop();

if __name__ == "__main__":
    main()