code: def _fill(self):
          
          r, g, b = hue2col(self._hue)
          width = self.winfo_width()
          height = self.winfo_height()
          h = float(height - 1)
          w = float(width - 1)
          if height:
              c = [(r + i / h * (255 - r), g + i / h * (255 - g), b + i / h * (255 - b)) for i in range(height)]
              data = []
              for i in range(height):
                  line = []
                  for j in range(width):
                      rij = round2(j / w * c[i][0])
                      gij = round2(j / w * c[i][1])
                      bij = round2(j / w * c[i][2])
                      color = rgb_to_hexa(rij, gij, bij)
                      line.append(color)
                  data.append("{" + " ".join(line) + "}")
              self.bg.put(" ".join(data))
docs: Create the gradient.