text: import numpy as np
  import matplotlib.pyplot as plt
  from scipy import optimize
  
  #直线方程函数
  def f_1(x, A, B):
      return A*x + B
  
  #二次曲线方程
  def f_2(x, A, B, C):
      return A*x*x + B*x + C
  
  #三次曲线方程
  def f_3(x, A, B, C, D):
      return A*x*x*x + B*x*x + C*x + D
  
  def plot_test():
  
      plt.figure()
  
      #拟合点
      x0 = [1, 2, 3, 4, 5]
      y0 = [1, 3, 8, 18, 36]
  
      #绘制散点
      plt.scatter(x0[:], y0[:], 25, "red")
  
      #直线拟合与绘制
      A1, B1 = optimize.curve_fit(f_1, x0, y0)[0]
      x1 = np.arange(0, 6, 0.01)
      y1 = A1*x1 + B1
      plt.plot(x1, y1, "blue")
  
      #二次曲线拟合与绘制
      A2, B2, C2 = optimize.curve_fit(f_2, x0, y0)[0]
      x2 = np.arange(0, 6, 0.01)
      y2 = A2*x2*x2 + B2*x2 + C2
      plt.plot(x2, y2, "green")
      # '''
      #三次曲线拟合与绘制
      A3, B3, C3, D3= optimize.curve_fit(f_3, x0, y0)[0]
      x3 = np.arange(0, 6, 0.01)
      y3 = A3*x3*x3*x3 + B3*x3*x3 + C3*x3 + D3
      plt.plot(x3, y3, "purple")
      # '''
      plt.title("test")
      plt.xlabel('x')
      plt.ylabel('y')
  
      plt.show()
  
      return
  plot_test()