plot

import matplotlib.pyplot as pl
import matplotlib.animation as animation
import numpy as np

x_min, x_max = 0, 500
y_min, y_max = 0, 500**3

def f1(x):
    return x**3

def f2(x):
    return 400*x**2

x = np.arange(0, 500, 1)
fig = pl.figure()
ax = pl.axes(xlim=(x_min, x_max), ylim=(y_min, y_max))

line1, = ax.plot([], [], lw=2, c='y', label="$x^3$")
line2, = ax.plot([], [], lw=2, c='b', label="$400x^2$")
lines = [line1, line2]

pl.legend(loc='upper left')

def init():
    line1.set_data([], [])
    line2.set_data([], [])
    return lines

def anima(i):
    x_frame = x[:i]
    y1_frame = f1(x_frame)
    y2_frame = f2(x_frame)
    
    line1.set_data(x_frame, y1_frame)
    line2.set_data(x_frame, y2_frame)
    
    return lines, 
    
anim = animation.FuncAnimation(fig, anima, init_func=init, frames=500, interval=25, blit=True)