Rotating a cube in python using tkinter

The while True loop never exits and is preventing the code to reach top.mainloop(), hence your canvas is never displayed.

You can replace it with a function that calls itself back using top.after method.

from tkinter import*import mathimport timeimport numpy as npclass Window(Frame):    def __init__(self, master=None):        Frame.__init__(self, master)        self.master = masterclass Square():    def __init__(self, length, cx, cy):        self._cx = cx        self._cy = cy        self._length = length        self._vertices = []        self._vertices.append([-length/2,length/2])        self._vertices.append([length/2, -length/2])        self._vertices.append([length/2, length/2])        self._vertices.append([-length/2, length/2])    def rotate(self, theta):        rotat_matrix = np.array([[math.cos(theta), math.sin(theta)],[-math.sin(theta), math.cos(theta)]])        #print("rotation matrix:", rotat_matrix)        for i in range(len(self._vertices)):            vector = np.dot(rotat_matrix,self. _vertices[i]).tolist()            #print("V:", vector)            self._vertices[i] = vectorsquare = Square(100, 500, 500)top = Tk()canvas = Canvas(top,bg="#EBEDEF",height=800, width=800)canvas.pack()def run():    v0 = square._vertices[0]    v1 = square._vertices[1]    v2 = square._vertices[2]    v3 = square._vertices[3]    canvas.create_line(v0[0] + 200, v0[1] + 200, v1[0]+200,v1[1]+200)    canvas.create_line(v1[0] + 200, v1[1] + 200, v2[0]+200,v2[1]+200)    canvas.create_line(v2[0] + 200, v2[1] + 200, v3[0]+200,v3[1]+200)    canvas.create_line(v3[0] + 200, v3[1] + 200, v0[0]+200,v0[1]+200)    square.rotate(math.pi/8)    print("rotated")    top.after(100, run)if __name__ == '__main__':    run()    top.mainloop()