python: How to monitor a variable ? Execute command when variable change

Question

I have a class like this

class WaveData(object):
    def __init__(self, data):
        self.data = data

and create a data object, plot a figure

wave = WaveData([[1, 2, 3], 
                 [7, 5, 6]])

import matplotlib.pyplot as plt
fig=plt.figure()
plot1, = fig.canvas.figure.subplots().plot(wave.data[0])
plot2, = fig.canvas.figure.subplots().plot(wave.data[1])

I hope when I change the wave value , plot will change synchronously

wave.data[1]=[5,6,7] # hope figure change together

I try to add method changedata for WaveData class, but:

1. it need use global variable fig , maybe not reasonale (I can put fig as self attribute , but in fact , the fig also link other class object which not written in here)
2. I cannot change fig by changing data directly: wave.data[1] =[5,6,7]

class WaveData(object):
    def __init__(self, data):
        self.data = data

    def changedata(self,value,index):
        self.data[index]=value
        

        #-- change the plot index th plot data--#
        global plot1,plot2,fig
        plot1.set_ydata(self.data[1])
        plot2.set_ydata(self.data[2])
        fig.canvas.draw_idle()
        #-- change the plot index th plot data--#
     

I want to create a watcher to monitor wave.data value . When detecte the value change , execute some action

How to do?

Answer 1

Right: plotting is not a dynamic or interactive process. You started the right way, with an access method to change the wave form. Now you have to re-plot and re-show the result ... which will possibly require closing the first plot manually, depending on the interface of your chosen drawing package (eg matplotlib ).

To get a fully interactive experience, you may want to use an animation package, such as PyGame, where changes in the visual display are part of the package assumptions.