Option for lazy evaluation st.download_button

[chrieke]

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?

[arkanoid]

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

[mathcatsand]

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:

Automatic Download / Select and Download File with Single Button Click

Hey @RyanMaley I figured it out! I simplified the JS to a one liner based on your reply. You can find it on here or modify the code below: import streamlit as st import streamlit.components.v1 as components import pandas as pd import base64 import json def download_button(object_to_download, download_filename): """ Generates a link to download the given object_to_download. Params: ------ object_to_download: The object to be downloaded. download_filename (str):…

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