def test():
for i in 'abc':
yield i
for i in [1, 2, 3]:
yield i
if __name__ == '__main__':
gen = test()
print(gen.send(None))
print(gen.send(None))
print(gen.send(None))
print(gen.send(None))
print(gen.send(None))
print(gen.send(None))
print(gen.send(None))def test():
for i in 'abc':
yield i
for i in [1, 2, 3]:
yield i
if __name__ == '__main__':
gen = test()
for i in gen:
print(i)使用for循环生成器，因为for循环可以捕捉StopIteration异常。
上面的代码也可以用yield from实现
def test():
yield from 'abc'
yield from [1, 2, 3]
if __name__ == '__main__':
gen = test()
for i in test():
print(i)yield from 后面需要加的是可迭代对象，它可以是普通的可迭代对象，也可以是迭代器，甚至是生成器。
使用yield from实现实时计算器
def average_gen():
"""
子生成器
"""
average = 0
total = 0
count = 0
while True:
num = yield average
if num is None:
break
count += 1
total += num
average = total / count
return average, count, total
def proxy_gen():
"""
委派生成器
"""
while True:
average, count, total = yield from average_gen()
print(f'平均值{average}, 计算{count}次, 总和{total}')
def client():
"""
调用端
"""
calc_average = proxy_gen()
calc_average.send(None)
# next(calc_average)
# 预激活协程
print(calc_average.send(10))
print(calc_average.send(20))
print(calc_average.send(30))
calc_average.send(None)
# 关闭协程
if __name__ == '__main__':
client()在委派生成器中的while True可以替换成for循环，循环的大小决定调用端可以calc_average.send(None)的次数(第一次预激活也计入)。
while True和for循环用来捕捉StopIteration异常，可以查看第一段代码。
示例
def average_gen():
"""
子生成器
"""
average = 0
total = 0
count = 0
while True:
num = yield average
if num is None:
break
count += 1
total += num
average = total / count
return average, count, total
def proxy_gen():
"""
委派生成器
"""
for i in range(2):
average, count, total = yield from average_gen()
print(f'平均值{average}, 计算{count}次, 总和{total}')
def client():
"""
调用端
"""
calc_average = proxy_gen()
calc_average.send(None)
# next(calc_average)
# 预激活协程
print(calc_average.send(10))
print(calc_average.send(20))
print(calc_average.send(30))
calc_average.send(None)
# 关闭协程
print(calc_average.send(10))
print(calc_average.send(20))
print(calc_average.send(30))
calc_average.send(None)
if __name__ == '__main__':
client()示例最后会抛出StopIteration异常。
因为在第二次calc_average.send(None)时，for循环捕捉了一次异常，进入了最后一次循环，在calc_average.send(None)时，for不能再次循环，不能处理StopIteration异常，故抛出。