python matplotlib: plotting in another process

Question

EDIT: The ultimate requirement for such a Python program is: Receive data from UART from a external circuitry (which probably is equipped with some sensors), the program wil

Answer 1

Made samll modifications to above code. I used Process, Queue, Value, Array in multiprocessing package to reduce the code complexity. Script will plot [0,0], [1,1], [2,2] etc on a graph

from multiprocessing import Process, Queue, Value, Array
import time
import matplotlib.pyplot as plt
from queue import Empty

def f(q, num, arr1, arr2):
    plt.ion()
    fig = plt.figure()
    fig = plt.figure(1)
    ax = fig.add_subplot(111)
    ax.margins(0.05, 0.05)

    #ax.set_autoscale_on(True)
    ax.autoscale(enable=True, axis='both')
    #ax.autoscale(enable=True, axis='y')
    ax.set_ylim(0, 100)
    line1, line2 = ax.plot([], [], 'b-', [], [], 'r-')


    while True :
        try:
            #val = q.get_nowait()
            val = q.get(timeout = 0.8) # reducing the timeout value will improve the response time on graph whie mouse is moved on it
            #val = q.get()
            if val == 'Exit':
                break
            if val == 'Go': 
                x = num.value
                #print("num.value = ", x)
                v1 = arr1[0:num.value]
                v2 = arr2[0:num.value]
                #print("v1 :", v1)
                #print("v2 :", v2)
                line1.set_xdata(range(1, len(v1) + 1, 1))
                line1.set_ydata(v1)
                line2.set_xdata(line1.get_xdata())
                line2.set_ydata(v2)

                ax.relim()
                ax.autoscale_view(tight=True, scalex=True, scaley=False)
                fig.canvas.draw()
                #print ("thread: DRAW")
                plt.pause(0.05)
        except Empty as e:
            x = num.value
            line1.set_xdata(range(1, len(v1) + 1, 1))
            line1.set_ydata(v1)
            line2.set_xdata(line1.get_xdata())
            line2.set_ydata(v2)

            ax.relim()
            ax.autoscale_view(tight=True, scalex=True, scaley=False)
            fig.canvas.draw()
            plt.pause(0.05)
            continue



if __name__ == '__main__':
    q = Queue()
    num = Value('i', 0)
    arr1 = Array('d', range(100))
    arr2 = Array('d', range(100))
    p = Process(target=f, args=(q,num, arr1, arr2, ))
    p.start()

    for i in range(10):
        arr1[i] = i
        arr2[i] = i 
        num.value = i+1
        q.put("Go")   # prints "[42, None, 'hello']"
        time.sleep(1)
    q.put("Exit")
    p.join()