如何嵌套任意数量的Python文件上下文管理器？

我想采用任意数量的路径来表示嵌套的tar档案,并对最里面的档案执行操作.问题是,嵌套可以是任意的,因此我需要的上下文管理器的数量也是任意的.

举个例子：

ARCHIVE_PATH = "path/to/archive.tar"

INNER_PATHS = (
    "nested/within/archive/one.tar","nested/within/archive/two.tar",# Arbitary number of these
)

def list_inner_contents(archive_path,inner_paths):
    with TarFile(archive_path) as tf1:
        with TarFile(fileobj=tf1.extractfile(inner_paths[0])) as tf2:
            with TarFile(fileobj=tf2.extractfile(inner_paths[1])) as tf3:
                # ...arbitary level of these!
                return tfX.getnames()

contents = list_inner_contents(ARCHIVE_PATH,INNER_PATHS))

我不能使用with语句的nesting syntax,因为可以有任意数量的级别来嵌套.我不能使用contextlib.nested因为文档在那里说：

…using nested() to open two files is a programming error as the first file will not be closed promptly if an exception is thrown when opening the second file.

有没有办法使用语言结构来执行此操作,还是需要手动管理我自己的打开文件对象堆栈？

最佳答案

对于这种情况,您可以使用递归.对于这种情况来说感觉最自然(当然如果在Python中没有特殊处理)：

ARCHIVE_PATH = "path/to/archive.tar"

INNER_PATHS = [
    "nested/within/archive/one.tar",# Arbitary number of these
]

def list_inner_contents(archive_path,inner_paths):
    def rec(tf,rest_paths):
        if not rest_paths:
            return tf.getnames()

        with TarFile(fileobj=tf.extractfile(rest_paths[0])) as tf2:
            return rec(tf2,rest_paths[1:])

    with TarFile(archive_path) as tf:
        try:
            return rec(tf,inner_paths)
        except RuntimeError:
            # We come here in case the inner_paths list is too long
            # and we go too deeply in the recursion
            return None