hello_triangle_glfw_begin_end.py

from OpenGL.GL import *
from OpenGL.GLU import *
from glfw.GLFW import *

attributes = [
#      x       y     z      R  G  B  A
    ((-0.866, -0.75, 0),   (1, 0, 0, 1)), 
    (( 0.866, -0.75, 0),   (1, 1, 0, 1)),
    (( 0,      0.75, 0),   (0, 0, 1, 1))
]

if glfwInit() == GLFW_FALSE:
    raise Exception("error: init glfw")

glfwWindowHint(GLFW_SAMPLES, 8)
window = glfwCreateWindow(640, 480, "OpenGL Window", None, None)
glfwMakeContextCurrent(window)

def size_callback(window, _w, _h):
    width, height = glfwGetFramebufferSize(window)
    glViewport(0, 0, width, height)
    aspect = width / height 
    glMatrixMode(GL_PROJECTION)
    glLoadIdentity()
    if aspect >= 1:
        glOrtho(-aspect, aspect, -1, 1, -1, 1)
    else:
        glOrtho(-1, 1, -1/aspect, 1/aspect, -1, 1)   
    glMatrixMode(GL_MODELVIEW)  
glfwSetWindowSizeCallback(window, size_callback)   
size_callback(window, 640, 480)

vendor, renderer = glGetString(GL_VENDOR).decode("utf-8"), glGetString(GL_RENDERER).decode("utf-8")
version, glsl_version = glGetString(GL_VERSION).decode("utf-8"), glGetString(GL_SHADING_LANGUAGE_VERSION).decode("utf-8")
major, minor = glGetInteger(GL_MAJOR_VERSION), glGetInteger(GL_MINOR_VERSION)
extensions = [glGetStringi(GL_EXTENSIONS, i) for i in range(glGetInteger(GL_NUM_EXTENSIONS))]
print(f"\n{vendor} / {renderer}\n  OpenGL: {version}\n  GLSL: {glsl_version}\n  Context {major}.{minor}\n")

@GLDEBUGPROC
def __CB_OpenGL_DebugMessage(source, type, id, severity, length, message, userParam):
    msg = message[0:length]
    print(msg.decode("utf-8"))
glDebugMessageCallback(__CB_OpenGL_DebugMessage, None)
errors_only = False
if errors_only:
    glDebugMessageControl(GL_DONT_CARE, GL_DONT_CARE, GL_DONT_CARE, 0, None, GL_FALSE)
    glDebugMessageControl(GL_DEBUG_SOURCE_API, GL_DEBUG_TYPE_ERROR, GL_DONT_CARE, 0, None, GL_TRUE)
else:
    glDebugMessageControl(GL_DONT_CARE, GL_DONT_CARE, GL_DONT_CARE, 0, None, GL_TRUE)
glEnable(GL_DEBUG_OUTPUT)
glEnable(GL_DEBUG_OUTPUT_SYNCHRONOUS)

glEnable(GL_MULTISAMPLE) # default
glEnable(GL_DEPTH_TEST)
glClearColor(0.0, 0.0, 0.0, 0.0)

while not glfwWindowShouldClose(window):
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT)
    glBegin(GL_TRIANGLES)
    for vertex, color in attributes:
        glColor4f(*color)
        glVertex3f(*vertex)
    glEnd()
    glfwSwapBuffers(window)
    glfwPollEvents()

glfwTerminate()
exit()