1. the use of matplotlib.pyplot is not hard to learn, which can be find on its official website. One of the common practices is

   import matplotlib as plt
   x = np.linspace(start,end,50)
   plt.plot(x,fun(x),ro)
   plt.show
   

   and this returns a graph of the function

2. any class that has a call method can be called with instance_name() just like a function

3. after importing the built-in module logging, the log-level can be altered to determine which kinds of messages shall be shown and which shall not. E.g.:logging.getLogger().setLevel(0) Another way is just print it out in a log-style, like

   print("[LOG] under current iteration: {}".format(summation))
   

4. do not start calculating until it’s called, so-called lazy mode

Source file avaliable at my github repo and ‘dalao’ smdsbz’s repo