ptyprocess.py 文件源码

def readline(self):
        """Read one line from the pseudoterminal, and return it as unicode.

        Can block if there is nothing to read. Raises :exc:`EOFError` if the
        terminal was closed.
        """
        try:
            s = self.fileobj.readline()
        except (OSError, IOError) as err:
            if err.args[0] == errno.EIO:
                # Linux-style EOF
                self.flag_eof = True
                raise EOFError('End Of File (EOF). Exception style platform.')
            raise
        if s == b'':
            # BSD-style EOF (also appears to work on recent Solaris (OpenIndiana))
            self.flag_eof = True
            raise EOFError('End Of File (EOF). Empty string style platform.')

        return s