如何利用蟒蛇封写回调函数

Question

我找到亚马逊的人页面上的代码。它被用作创建可作为transfer module的上传功能的参数传递的回调对象：

class ProgressPercentage(object):

def __init__(self, filename):
    self._filename = filename
    self._size = float(os.path.getsize(filename))
    self._seen_so_far = 0
    self._lock = threading.Lock()

def __call__(self, bytes_amount):
    # To simplify we'll assume this is hooked up
    # to a single filename.
    with self._lock:
        self._seen_so_far += bytes_amount
        percentage = (self._seen_so_far / self._size) * 100
        sys.stdout.write(
            "\r%s  %s / %s  (%.2f%%)" % (
                self._filename, self._seen_so_far, self._size,
                percentage))
        sys.stdout.flush()

一类用于保持必需的后续调用（即self.seen_so_far）的状态

有没有办法重新实现此作为取蟒蛇封闭的优势，以确保有状态的功能？

Answer 1

当然，一个简单的音译会是这样的：

def ProgressPrecentage(filename):
    size = os.path.getsize(filename)
    seen_so_far = 0
    lock = threading.Lock()
    def worker(bytes_amount):
        nonlocal seen_so_far
        with lock:
            seen_so_far += bytes_amount
            percentage = (seen_so_far / size)*100
            msg = "\r%s  %s / %s  (%.2f%%)" % (
                filename, seen_so_far, size, percentage
            )
            sys.stdout.write(msg)
            sys.stdout.flush()
    return worker