This is a simple example of how to use Matplotlib and Python to create a realtime graph of incoming data (simulated in the example).

realtime-graph.py

import matplotlib.pyplot as plt
import matplotlib.animation as anim
from collections import deque
import random

MAX_X = 100   #width of graph
MAX_Y = 1000  #height of graph

# intialize line to horizontal line on 0
line = deque([0.0]*MAX_X, maxlen=MAX_X)

def update(fn, l2d):
    #simulate data from serial within +-5 of last datapoint
    dy = random.randint(-5, 5)
    #add new point to deque
    line.append(line[MAX_X-1]+dy)
    # set the l2d to the new line coords
    # args are ([x-coords], [y-coords])
    l2d.set_data(range(-MAX_X/2, MAX_X/2), line)

fig = plt.figure()
# make the axes revolve around [0,0] at the center
# instead of the x-axis being 0 - +100, make it -50 - +50
# ditto for y-axis -512 - +512
a = plt.axes(xlim=(-(MAX_X/2),MAX_X/2), ylim=(-(MAX_Y/2),MAX_Y/2))
# plot an empty line and keep a reference to the line2d instance
l1, = a.plot([], [])
ani = anim.FuncAnimation(fig, update, fargs=(l1,), interval=50)


plt.show()