tarfile.py 文件源码

def extractfile(self, member):
        """Extract a member from the archive as a file object. `member' may be
           a filename or a TarInfo object. If `member' is a regular file, a
           file-like object is returned. If `member' is a link, a file-like
           object is constructed from the link's target. If `member' is none of
           the above, None is returned.
           The file-like object is read-only and provides the following
           methods: read(), readline(), readlines(), seek() and tell()
        """
        self._check("r")

        if isinstance(member, basestring):
            tarinfo = self.getmember(member)
        else:
            tarinfo = member

        if tarinfo.isreg():
            return self.fileobject(self, tarinfo)

        elif tarinfo.type not in SUPPORTED_TYPES:
            # If a member's type is unknown, it is treated as a
            # regular file.
            return self.fileobject(self, tarinfo)

        elif tarinfo.islnk() or tarinfo.issym():
            if isinstance(self.fileobj, _Stream):
                # A small but ugly workaround for the case that someone tries
                # to extract a (sym)link as a file-object from a non-seekable
                # stream of tar blocks.
                raise StreamError("cannot extract (sym)link as file object")
            else:
                # A (sym)link's file object is its target's file object.
                return self.extractfile(self._find_link_target(tarinfo))
        else:
            # If there's no data associated with the member (directory, chrdev,
            # blkdev, etc.), return None instead of a file object.
            return None