Draw plot in real time with matplotlib

rt-draw.py

#!/usr/bin/env python3
# -*- coding: utf-8 -*-
#
# Copyright (C) 2014 Savoir-Faire Linux Inc.
# Authors:
# Sebastien Bourdelin <sebastien.bourdelin@savoirfairelinux.com>
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License Version 2 as
# published by the Free Software Foundation.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program. If not, see <http://www.gnu.org/licenses/>.

import sys, argparse
import numpy as np
import matplotlib.pyplot as plt
import matplotlib.animation as animation
import re

# The update graph function
def animate(data):
    global x_max, x_min, x, y

    try:
        # we must recalculate the abscissa range
        x_new = float(data)
        if x_max is None or x_new > x_max:
            x_max = x_new
        if x_min is None or x_new < x_min:
            x_min = x_new
        ax.set_xlim(x_min, x_max)

        # add the new plot coordinate
        x.append(x_new)
        y.append(0)
        line.set_data(x, y)

        return line,

    except KeyboardInterrupt:
        print("leaving...")

# The data generator take its
# input from file or stdin
def data_gen():
    while True: 
        line = fd.readline().strip()
        if line:
            yield line

if __name__ == '__main__':
    parser = argparse.ArgumentParser()
    parser.add_argument('--file', dest='filename')
    args = parser.parse_args()

    if args.filename:
        fd = open(args.filename, encoding='utf-8')
    else:
        fd = sys.stdin

    fig = plt.figure()
    ax  = fig.add_subplot(111)

    line, = ax.plot([], [], 'ro') 
    x_min = x_max = None
    x = []
    y = []
    ax.set_ylim(-1, 1)

    anim = animation.FuncAnimation(fig, animate, frames=data_gen, repeat=False)

    plt.show()