[ Python ]如何取回生成器的返回值

def iter_check(filepath: str | bytes | os.PathLike[str | bytes], algorithm_name: str, checksum: str):
    algorithm = get_algorithm(algorithm_name)
    with open(filepath, mode='rb') as file:
        algorithm_instance = algorithm()
        for block in iter(partial(file.read, 1024), b''):
            yield block
            algorithm_instance.update(block)
    return algorithm_instance.hexdigest() == checksum

其本质上是一个生成器，每一次迭代都会yield一个block。那么，能否取回最后由return返回的校验结果？

str

block

checksum

生成器

3 条回复 • 2021-09-25 06:53:40 +08:00

chenstack

2021-09-21 00:58:04 +08:00

生成器迭代结束后会生成一个 StopIteration，返回值就是这个 StopIteration 的 value
def iter_check():
    for i in range(5):
        yield i
    return 10

checker = iter_check()
while True:
    try:
        print(next(checker))
    except StopIteration as e:
        print("result: ", e.value)
        break

BBCCBB

2021-09-21 09:41:01 +08:00

for 循环, 或者看一下 next 函数的用法.

O5oz6z3

2021-09-25 06:53:40 +08:00

基本原理已经被楼上说完了，至于你的需求可以很容易想到一个简单的实现，不知道有没有现成的：
class wrapiter:
... def __init__(self, _iter):
... ... self.iter = iter(_iter)
... ... self.val = None
... def __iter__(self):
... ... return self
... def __next__(self):
... ... try:
... ... ... return next(self.iter)
... ... except StopIteration as e:
... ... ... self.val = e.value
... ... ... raise

it = wrapiter(range(9))
print([x for x in it])
print(it.val)