strip_chart_demo - GitPress.io

Example Python program strip_chart_demo.py

Modules

from kivy.app import App
from kivy.uix.widget import Widget
from kivy.uix.boxlayout import BoxLayout
import matplotlib
import kivy.garden.matplotlib.backend_kivy
from kivy.garden.matplotlib import FigureCanvasKivy, FigureCanvasKivyAgg
from matplotlib.backends.backend_agg import FigureCanvasAgg
import numpy as np
from matplotlib.lines import Line2D
import matplotlib.pyplot as plt
import matplotlib.animation as animation

Classes

class Scope(object):
class MyApp(App):

Methods

def init(self, ax, maxt=2, dt=0.02):
def update(self, y):
def emitter(p=0.03):
def build(self):
def on_start(self, *args):

Code

Python example

"""
Emulate an oscilloscope.  Requires the animation API introduced in
matplotlib 1.0 SVN.
"""
from kivy.app import App
from kivy.uix.widget import Widget
from kivy.uix.boxlayout import BoxLayout

import matplotlib
matplotlib.use("module://kivy.garden.matplotlib.backend_kivy")
import kivy.garden.matplotlib.backend_kivy
from kivy.garden.matplotlib import FigureCanvasKivy, FigureCanvasKivyAgg
from matplotlib.backends.backend_agg import FigureCanvasAgg

import numpy as np
from matplotlib.lines import Line2D
import matplotlib.pyplot as plt
import matplotlib.animation as animation


class Scope(object):
    def __init__(self, ax, maxt=2, dt=0.02):
        self.ax = ax
        self.dt = dt
        self.maxt = maxt
        self.tdata = [0]
        self.ydata = [0]
        self.line = Line2D(self.tdata, self.ydata)
        self.ax.add_line(self.line)
        self.ax.set_ylim(-.1, 1.1)
        self.ax.set_xlim(0, self.maxt)

    def update(self, y):
        lastt = self.tdata[-1]
        if lastt > self.tdata[0] + self.maxt:  # reset the arrays
            self.tdata = [self.tdata[-1]]
            self.ydata = [self.ydata[-1]]
            self.ax.set_xlim(self.tdata[0], self.tdata[0] + self.maxt)
            self.ax.figure.canvas.draw()

        t = self.tdata[-1] + self.dt
        self.tdata.append(t)
        self.ydata.append(y)
        self.line.set_data(self.tdata, self.ydata)
        return self.line,


def emitter(p=0.03):
    'return a random value with probability p, else 0'
    while True:
        v = np.random.rand(1)
        if v > p:
            yield 0.
        else:
            yield np.random.rand(1)


class MyApp(App):

    def build(self):
        return Widget()

    def on_start(self, *args):

        fig, ax = plt.subplots()
        scope = Scope(ax)

        # pass a generator in "emitter" to produce data for the update func
        ani = animation.FuncAnimation(fig, scope.update, emitter, interval=10,
                                      blit=True)
        plt.show()


if __name__ == "__main__":
    app = MyApp()
    app.run()

Useful Links

Articles: https://python-commandments.org/
Python shell: https://bsdnerds.org/learn-python/
Tutorial: https://pythonprogramminglanguage.com/