Support for passing a list[ImageUrl] to chatprompt

[ashwin153]

I want to write a function like:

@magentic.chatprompt(
    magentic.UserMessage([
        # how do i include images here?
    ]),
)
def generate_something(images: list[magentic.ImageUrl])

But I'm struggling with figured out how to embed the list of images.

The workaround is to use magentic.Chat, but then I have to implement retries and stuff myself. Any ideas? @jackmpcollins

[jackmpcollins]

Hi @ashwin153 Currently there's no way to provide a dynamic number of images. If it's always the same number of images you can use Placeholder for each one.
https://magentic.dev/vision/#placeholder

To fix this in magentic I think would just require handling if isinstance(self.content, Placeholder) in

magentic/src/magentic/chat_model/message.py

Lines 239 to 248 in 50c7aee

	def format(
	self: "UserMessage[StrT | NonStringSequence[StrT2 | UserMessageContentBlockT | Placeholder[UserMessageContentBlockT2]]]",
	**kwargs: Any,
	) -> "UserMessage[StrT | Sequence[StrT2 | UserMessageContentBlockT | UserMessageContentBlockT2]]":
	if isinstance(self.content, str):
	return UserMessage(self.content.format(**kwargs))
	if isinstance(self.content, Iterable):
	return UserMessage([block.format(**kwargs) for block in self.content]) # type: ignore[misc]
	msg = f"Unsupported content type: {type(self.content)}"
	raise ValueError(msg)

That would allow you to do UserMessage(Placeholder(list[ImageUrl], "images"))