Python的生成器函数详解

g1 = (x*2 for x in range(5))
next(g1)
0
next(g1)
2
...

def g2():
    for x in range(5):
        yield x*2

list(g2)
[0, 2, 4, 6, 8]

def inc1():
    for x in range(10000):
        yield x

def inc2():
    yield from range(10000)

list01 = [4,54,65,6,76,87,9]

#传统方式
def get_even01():
	#做一个容器来存储数据
	result = []
	for item in list01:
		if item % 2 == 0:
			result.append(item)
	return result

re = get_even01()
for item in re:
	print(item)

#使用生成器技术
def get_even02():
	for item in list01:
		if item % 2 == 0:
			yield item	#yield是生成器的关键词

re = get_even02()	#返回一个生成器对象
for item in re:	#使用for来迭代re,因为生成器也是可迭代对象(有__iter__()方法)
	print(item)

def f1():
	for i in range(2):
		yield i
		
g = f1()	

print(g.__next__())	#0
print(g.__next__())	#1
print(g.__next__())	#抛出异常StopIteration

#为了不抛出异常，改写上面的代码
def f1():
	for i in range(2):
		yield i
g = f1()
while True:
	try:
		print(g.__next__())
	except Exception as e:	#捕获异常，结束循环
		break