st.write_stream support for code

[sircambridge]

Checklist

• [X] I have searched the existing issues for similar feature requests.
• [X] I added a descriptive title and summary to this issue.

Summary

there should be a st.write_code_stream, that can stream code properly formatted while fading in with the typewriter effect.

Why?

the new st.write_stream is awesome! it works very well with langchain when using chain.stream as a generator that yields chunks. However, when using an LLM to generate code - which is often the case, comments starting with "#" and indentations trigger markdown formatting and blocks, making the code generation stream a janky mess. there is no stream version of st.text either, so there doesnt seem to be a way to stream code without causing the flashing janky mess.

How?

st.write_stream_code()

Additional Context

No response

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[Asaurus1]

I also want this! And am happy to add it if product approves.

[CHerSun]

Can't you just st.write to st.empty on new chunk?

[Asaurus1]

Can't you just st.write to st.empty on new chunk?

Yep, I've done this in some places. You can store the result of every generator yield in a buffer and then write the entire contents of the buffer to an empty DeltaGenerator every update / newline. But that does stop working well for longer output because it means you're sending the entire buffer string over the network for each update.

[sircambridge]

Agree! Using write and empty periodically is a pretty good idea, especially if its smart about yielding not every single token but maybe every 0.2 seconds or n number of tokens. I'll give this a try

However the syntax highlighting would be a super nice to have.

[Asaurus1]

You get the syntax highlighting if you call st.code instead of write.

[haberchr]

Would there be anything more to minimally support this than adding a flag argument to write_stream(), and switching markdown() to text() here according to whether the flag is activated?: https://github.com/streamlit/streamlit/blob/develop/lib/streamlit/elements/write.py#L156

The better solution would be to add a new function text_stream() to https://github.com/streamlit/streamlit/blob/develop/lib/streamlit/elements/text.py basically the same as write_stream(), except replacing markdown() with text() everywhere. However, I imagine support for this new function name would need to be added in many places in the code.

I believe it's currently impossible to render the streamed input as code even with custom CSS until the markdown function is turned off.

This seems like a really useful feature. Is there any movement on this?