<p>The following uses ctypes to get to the OpenGL 1.5/2.0 functions not exported by PyOpenGL.</p>
<p>See [[GLSL_ARB_Example]] for an implementation using the OpenGL ARB extensions.</p>
<code>
from ctypes import *
import sys

import pygame
from pygame.locals import *

try:
    # For OpenGL-ctypes
    from OpenGL import platform
    gl = platform.OpenGL
except ImportError:
    try:
        # For PyOpenGL
        gl = cdll.LoadLibrary('libGL.so')
    except OSError:
        # Load for Mac
        from ctypes.util import find_library
        # finds the absolute path to the framework
        path = find_library('OpenGL')
        gl = cdll.LoadLibrary(path)

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

glCreateShader = gl.glCreateShader
glShaderSource = gl.glShaderSource
glShaderSource.argtypes = [c_int, c_int, POINTER(c_char_p), POINTER(c_int)]
glCompileShader = gl.glCompileShader
glGetShaderiv = gl.glGetShaderiv
glGetShaderiv.argtypes = [c_int, c_int, POINTER(c_int)]
glGetShaderInfoLog = gl.glGetShaderInfoLog
glGetShaderInfoLog.argtypes = [c_int, c_int, POINTER(c_int), c_char_p]
glDeleteShader = gl.glDeleteShader
glCreateProgram = gl.glCreateProgram
glAttachShader = gl.glAttachShader
glLinkProgram = gl.glLinkProgram
glGetError = gl.glGetError
glUseProgram = gl.glUseProgram

GL_FRAGMENT_SHADER = 0x8B30
GL_VERTEX_SHADER = 0x8B31
GL_COMPILE_STATUS = 0x8B81
GL_LINK_STATUS = 0x8B82
GL_INFO_LOG_LENGTH = 0x8B84

def compile_shader(source, shader_type):
    shader = glCreateShader(shader_type)
    source = c_char_p(source)
    length = c_int(-1)
    glShaderSource(shader, 1, byref(source), byref(length))
    glCompileShader(shader)
    
    status = c_int()
    glGetShaderiv(shader, GL_COMPILE_STATUS, byref(status))
    if not status.value:
        print_log(shader)
        glDeleteShader(shader)
        raise ValueError, 'Shader compilation failed'
    return shader

def compile_program(vertex_source, fragment_source):
    vertex_shader = None
    fragment_shader = None
    program = glCreateProgram()

    if vertex_source:
        vertex_shader = compile_shader(vertex_source, GL_VERTEX_SHADER)
        glAttachShader(program, vertex_shader)
    if fragment_source:
        fragment_shader = compile_shader(fragment_source, GL_FRAGMENT_SHADER)
        glAttachShader(program, fragment_shader)

    glLinkProgram(program)

    if vertex_shader:
        glDeleteShader(vertex_shader)
    if fragment_shader:
        glDeleteShader(fragment_shader)

    return program

def print_log(shader):
    length = c_int()
    glGetShaderiv(shader, GL_INFO_LOG_LENGTH, byref(length))

    if length.value > 0:
        log = create_string_buffer(length.value)
        glGetShaderInfoLog(shader, length, byref(length), log)
        print >> sys.stderr, log.value
</code>
<p>Example usage (draws a spinning teapot coloured by a fragment shader, using a pass-through vertex shader):</p>
<code>
if __name__ == '__main__':
    glutInit(sys.argv)
    width, height = 640, 480
    pygame.init()
    pygame.display.set_mode((width, height), OPENGL | DOUBLEBUF)

    program = compile_program('''
    // Vertex program
    varying vec3 pos;
    void main() {
        pos = gl_Vertex.xyz;
        gl_Position = gl_ModelViewProjectionMatrix * gl_Vertex;
    }
    ''', '''
    // Fragment program
    varying vec3 pos;
    void main() {
        gl_FragColor.rgb = pos.xyz;
    }
    ''')

    glMatrixMode(GL_PROJECTION)
    glLoadIdentity()
    gluPerspective(90.0, width/float(height), 1.0, 100.0)
    glMatrixMode(GL_MODELVIEW)
    glEnable(GL_DEPTH_TEST)
    
    quit = False
    angle = 0
    while not quit:
        for e in pygame.event.get():
            if e.type in (QUIT, KEYDOWN):
                quit = True
        glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT)
        glLoadIdentity()
        glTranslate(0.0, 0.0, -2.5)
        glRotate(angle, 0.0, 1.0, 0.0)
        glUseProgram(program)
        glutSolidTeapot(1.0)
        angle += 0.1 
        pygame.display.flip()
</code>
<p>Here's another shader that does "cartoon" shading. It was adapted from <a href="http://www.lighthouse3d.com/opengl/glsl/index.php?toon2"> here </a>. It works off of the position of GL_LIGHT0. It doesn't actually use any parameters of the light, so you could actually just set a parameter with the "light" position. The two shaders are:</p>
<code>
    // Vertex program
    varying vec3 normal;
    void main() {
        normal = gl_NormalMatrix * gl_Normal;
        gl_Position = gl_ModelViewProjectionMatrix * gl_Vertex;
    }
</code>
<code>
    // Fragment program
    varying vec3 normal;
    void main() {
        float intensity;
        vec4 color;
        vec3 n = normalize(normal);
        vec3 l = normalize(gl_LightSource[0].position).xyz;

        // quantize to 5 steps (0, .25, .5, .75 and 1)
        intensity = (floor(dot(l, n) * 4.0) + 1.0)/4.0;
        color = vec4(intensity*1.0, intensity*0.5, intensity*0.5,
            intensity*1.0);

        gl_FragColor = color;
    }
</code>