code: #用python绘制坐标
  #https://matplotlib.org/examples/axes_grid/demo_axisline_style.html
  #https://stackoverflow.com/questions/13430231/how-i-can-get-cartesian-coordinate-system-in-matplotlib
  #https://stackoverflow.com/questions/50798265/what-is-subplotzero-documentation-lacking
  
  # notice import as 和 from import有什么区别？
  import numpy as np
  import matplotlib.pyplot as plt
  
  from matplotlib.axes import Axes
  from matplotlib.figure import Figure
  from bak.basic_units import cm
  
  fig: Figure = plt.figure()
  # notice 得到并设置坐标坐标系
  ax: Axes = fig.subplots()
  ax.set_title('x axis spine at zero data coordinate')
  ax.set_xlabel("Axes zero")
  ax.set_ylabel("Y")
  ax.axis()
  ax.spines['top'].set_visible(False)
  ax.spines['right'].set_visible(False)
  ax.set_xlim(-3, 10)
  ax.set_ylim(-3, 10)
  
  # todo 设定坐标轴的样式和刻度
  yAxis: Axes = ax.spines['left']
  yAxis.set_position(('data', 0))
  xAxis: Axes = ax.spines['bottom']
  xAxis.set_position(('data', 0))
  #xAxis.set_axisline_style("-|>")
  
  # notice 设定x的范围
  x = np.arange(-1, 3, 0.01)
  # notice 绘制图形
  ax.plot(x, 2*x, xunits=cm, yunits=cm)
  
  plt.show()
  
apis: numpy.arange matplotlib.pyplot.figure matplotlib.pyplot.show