Option for lazy evaluation st.download_button

Using Streamlit
1

Hi there st team!

I want to give the user an option to download an image via st.download_button, but only render the image in case the button is clicked (expensive render). I was thinking there should be some option so that only clicking the button evaluates what would be downloaded, e.g.

st.download_button(label="Download image", data=render_function, file_name="image.png", lazy=True)

The only workaround I can think off right now is sticking the download-button inside a regular button (obviously super ugly), or a custom download button implementation. Any other ideas?

4 Likes
2

I’m stuck with same issue. Any news on this?

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The download button needs to be passed the data upon rendering the button, so if you want to delay the gathering/compiling of that data then you may be forced into using a custom component or script injection.

Here is a post about scripting a download from just before the download button existed so you can modify it to your needs:

Here’s the associated gist: autodownload-csv.py · GitHub

And here’s a GitHub feature request you can vote on to get the requested functionality added to the download button in Streamlit: Defered data for download button · Issue #5053 · streamlit/streamlit · GitHub

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