Currently, it seems that code within an expander is run every time the script is rerun, regardless of whether it’s collapsed or expanded, which is definitely very useful in a lot of circumstances, but I was wondering if this could be turned off in any way, for example to avoid performing expensive computation if the user isn’t interested in the result.
Is there maybe a way to access the state of the expander, so that you can tell programmatically whether it’s expanded or collapsed at any given time (then conditionally perform the computation)? Otherwise, would it be possible to add an option in the expander to disable the code within the expander when it’s collapsed?
Below is a simple example of the kind of thing I was trying to accomplish. For now, I’m just using a checkbox to enable/disable the computation, but of course the expander is a lot nicer, so it would be great to be able to achieve this with the expander.
import streamlit as st import numpy as np import time @st.cache() def get_images(): return np.random.random((10,300,300,3)) @st.cache() def do_expensive_computation(image): time.sleep(3) return image images = get_images() num = st.slider('Image number', min_value=1, max_value=images.shape) col1, col2 = st.beta_columns(2) with col1: st.subheader('Image') st.image(images[num-1]) with col2: result_expander = st.beta_expander('Optional result', expanded=False) with result_expander: # ideally only execute this code when expanded result = do_expensive_computation(images[num-1]) st.image(result)