提醒：只是笔记，不是教程，仅仅供本人后期回顾用。

•   serializer = SnippetSerializer(data=data)
    serializer.is_valid()
    # True
    serializer.validated_data
    serializer.save()
    # <Snippet: Snippet object>
  

• 通过data初始化一个serializer实例后，在访问serializer.validated_data和serializer.data之前必须调用is_valid()函数；在访问了serializer.data后无法调用serializer.save(),如下代码错误：

  serializer = SnippetSerializer(data=data)
  serializer.is_valid()
  # True
  serializer.data
  serializer.save()
  # AssertionError: You cannot call `.save()` after accessing
  # `serializer.data`.If you need to access data before committing
  #to the database then inspect 'serializer.validated_data' instead.