OpenGL.error.NullFunctionError: Attempt to call an undefined function glutInitDisplayMode

try:
  from OpenGL.GLUT import *
  from OpenGL.GL import *
  from OpenGL.GLU import *
except:
  print('ERROR: PyOpenGL not installed properly.')
  import sys
  sys.exit()
 
 
global xrot
global yrot
global ambient
global greencolor
global treecolor
global lightpos
 
def init():
    global xrot
    global yrot
    global ambient
    global greencolor
    global treecolor
    global lightpos
 
    xrot = 0.0
    yrot = 0.0
    ambient = (1.0, 1.0, 10, 1)
    greencolor = (0.2, 0.8, 0.0, 0.8)
    treecolor = (0.9, 0.6, 0.3, 0.8)
    lightpos = (1.0, 1.0, 1.0)
 
    glClearColor(0.5, 0.5, 0.5, 1.0)
    gluOrtho2D(-1.0, 1.0, -1.0, 1.0)
    glRotatef(-90, 1.0, 0.0, 0.0)
    glLightModelfv(GL_LIGHT_MODEL_AMBIENT, ambient)
    glEnable(GL_LIGHTING)
    glEnable(GL_LIGHT0)
    glLightfv(GL_LIGHT0, GL_POSITION, lightpos)
 
def specialkeys(key, x, y):
    global xrot
    global yrot
 
    if key == GLUT_KEY_UP:
        xrot -= 2.0
    if key == GLUT_KEY_DOWN:
        xrot += 2.0
    if key == GLUT_KEY_LEFT:
        yrot -= 2.0
    if key == GLUT_KEY_RIGHT:
        yrot += 2.0
 
    glutPostRedisplay()
 
def draw():
    global xrot
    global yrot
    global greencolor
    global treecolor
    global lightpos
 
    glClear(GL_COLOR_BUFFER_BIT)
    glPushMatrix()
    glRotatef(xrot, 1.0, 0.0, 0.0)
    glRotatef(yrot, 0.0, 1.0, 0.0)
    glLightfv(GL_LIGHT0, GL_POSITION, lightpos)
 
    glMaterialfv(GL_FRONT_AND_BACK, GL_DIFFUSE, treecolor)
    glTranslatef(0.0, 0.0, -0.7)
 
    glutSolidCylinder(0.1, 0.2, 20, 20)
 
    glMaterialfv(GL_FRONT_AND_BACK,GL_DIFFUSE, greencolor)
    glTranslatef(0.0, 0.0, 0.2)
 
    glutSolidCone(0.5, 0.5, 20, 20)
    glTranslatef(0.0, 0.0, 0.3)
    glutSolidCone(0.4, 0.4, 20, 20)
    glTranslatef(0.0, 0.0, 0.3)
    glutSolidCone(0.3, 0.3, 20, 20)
 
    glPopMatrix()
    glutSwapBuffers()
 
#try:
glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB)
glutInitWindowSize(300, 300)
glutInitWindowPosition(50, 50)
glutInit(sys.argv)
glutCreateWindow(b"Happy New Year!")
glutDisplayFunc(draw)
glutSpecialFunc(specialkeys)
init()
glutMainLoop()
#except:
    #print('Not work! Why?!?!?!')