Purpose of NullMediaItem

The NullMediaItem class represents the absence of media (image, audio, or video) in a way that avoids special-case handling elsewhere in the code.

It follows the Null Object Pattern , which provides a default behavior for "no object" cases, eliminating the need for repetitive if media is not None or if media: checks in templates or logic.

Why use it?

Without NullMediaItem:

if question.media:
    for m in question.media:
        if m.type == "image":
            ...

With NullMediaItem:

for m in question.media:
    html += m.to_html()

→ no conditional logic needed – every MediaItem, even the null variant, understands how to behave.

Behavior of NullMediaItem

Method	Behavior
type()	Returns "none"
to_dict()	Returns empty {} or None
to_html()	Returns "" (empty string)

When is it used?

You can attach one or more NullMediaItem()s to a Question instead of using None, [], or omitting the field entirely.

For example:

{{{|!python question = TextQuestion(

qid="q1", text="What is your name?", media=[NullMediaItem()]

) }}}

This way, the rendering pipeline stays uniform, regardless of whether media is present or not.

Benefits

• Simplifies templates and rendering logic

• Eliminates null checks in UI code

• Makes polymorphism clean and consistent

• Encourages Tell, Don't Ask design (don’t ask “do you have media?”, just tell media to render itself)