Animation — FuncAnimation

import numpy as np
import matplotlib.pyplot as plt
from matplotlib.animation import FuncAnimation
 
fig, ax = plt.subplots()
ax.set_xlim(0, 2*np.pi)         # Why: set limits ONCE so blitting can cache background
ax.set_ylim(-1.1, 1.1)
x = np.linspace(0, 2*np.pi, 400)
line, = ax.plot([], [], lw=2)   # Why: create the artist ONCE, empty for now
 
def init():
    line.set_data([], [])       # Why: clean background; defines what "before frame 0" looks like
    return line,                # Why: blit needs the changed artists
 
def update(frame):              # frame = 0,1,2,... from frames=...
    y = np.sin(x - 0.1*frame)   # Why: shift phase by frame → wave moves right
    line.set_data(x, y)         # Why: MUTATE existing artist, don't create a new one
    return line,                # Why: tell blit what to redraw
 
anim = FuncAnimation(fig, update, frames=200, init_func=init,
                     interval=20, blit=True)   # 1000/20 = 50 FPS
plt.show()
# anim.save("wave.mp4", fps=50)  # or "wave.gif"

def frame_gen():                 # Why: when each frame needs custom values, not just 0..N
    t = 0.0
    while t < 6.28:
        yield t                  # this value becomes `frame` in update
        t += 0.05
 
def update(t):
    line.set_data(x, np.sin(x - t))
    return line,
 
anim = FuncAnimation(fig, update, frames=frame_gen,
                     init_func=init, interval=30, blit=True, save_count=200)

line, = ax.plot([], [], 'b-')
dot,  = ax.plot([], [], 'ro')
 
def update(i):
    xi = x[:i]
    line.set_data(xi, np.sin(xi))    # growing trail
    dot.set_data([x[i]], [np.sin(x[i])])  # Why: lists, because set_data wants sequences
    return line, dot                 # Why: return ALL changed artists for blit