[Matplotlib-users] animation.FuncAnimation example --- how does it work?

[Virgil S. <vs...@it...>]

The following interesting example (random_data.py) is posted at:

http://matplotlib.org/1.4.2/examples/animation/random_data.html


import matplotlib.pyplot as plt
import matplotlib.animation as animation

fig, ax = plt.subplots()
line, = ax.plot(np.random.rand(10))
ax.set_ylim(0, 1)

def update(data):
     line.set_ydata(data)
     return line,

def data_gen():
     while True: yield np.random.rand(10)

ani = animation.FuncAnimation(fig, update, data_gen, interval=100)
plt.show()

This codes works; but, I am very confused by it. For example:

1. There are 3 positional arguments given for animation.FuncAnimation; but, in the
API documentation for this class (http://matplotlib.org/api/animation_api.html), 
only
two positional arguments are shown.

2. data, the argument to the update function seems to be undefined.

I would appreciate an explanation (in some detail) of how this code actually works.