calculated.py 文件源码

def render(self, ctx=None):
        '''
        Render the current value into a :class:`bitstring.Bits` object

        :rtype: :class:`bitstring.Bits`
        :return: the rendered field
        '''
        self._initialize()
        if ctx is None:
            ctx = RenderContext()
        #
        # if we are called from within render, return a dummy object...
        #
        if self in ctx:
            self._current_rendered = self._in_render_value()
        else:
            ctx.push(self)
            if self.dependency_type == Calculated.VALUE_BASED:
                self._rendered_field = self._field.render(ctx)
            self._render()
            ctx.pop()
        return self._current_rendered