Effective python – 例33 在巢狀generators 使用yield from

def move(period, speed):
    for _ in range(period):
        yield speed

def pause(delay):
    for _ in range(delay):
        yield 0

def animate():
    for delta in move(4, 5.0):
        yield delta
    for delta in pause(3):
        yield delta
    for delta in move(2, 3.0):
        yield delta

def render(delta):
    print(f'Delta: {delta:.1f}')
    # Move the imgaes onscreen
    ...

def run(func):
    for delta in func():
        render(delta)

run(animate)

想像我們在螢幕上用不同速度輪播不同照片來做成動畫，有的時候也會在中間暫停一下。

Delta: 5.0
Delta: 5.0
Delta: 5.0
Delta: 5.0
Delta: 0.0
Delta: 0.0
Delta: 0.0
Delta: 3.0
Delta: 3.0

改用yield from不僅是看起來更簡潔，重點是可以獲得更佳的運算效能。

def animate_composed():
    yield from move(4, 5.0)
    yield from pause(3)
    yield from move(2, 3.0)

run(animate_composed)