streams.py 文件源码

def seek(self, offset, whence=io.SEEK_SET):
        """Change the file position.

        The new position is specified by offset, relative to the
        position indicated by whence. Values for whence are:

            0: start of stream (default); offset must not be negative
            1: current stream position
            2: end of stream; offset must not be positive

        Returns the new file position.

        Note that seeking is emulated, so depending on the parameters,
        this operation may be extremely slow.
        """
        with self._lock:
            self._check_can_seek()
            return self._buffer.seek(offset, whence)