Widget's new value goes to limbo with st.experimental_get/set_query_params

Summary

I am using query_params to mirror state of widgets, so I am able to reproduce specific state with URL. I need to change state of each widget twice to get change.

Steps to reproduce

1. Load state from URL with st.experimental_get_query_params

query_state = st.experimental_get_query_params()

1. Set previous state as preselected value to st.radio

    select_options = ['All', 'Case ID', 'Cedant', 'Doc Type']
    if 'select_aggregation' in query_state:
        preselected_index = find_index(select_options, lambda item: item == query_state['select_aggregation'][0])
    else:
        preselected_index = 0
    select_aggregation = st.sidebar.radio(
        label='Group by:',
        options=select_options,
        index=preselected_index if preselected_index > -1 else 0
    )

1. Store current value to query params

st.experimental_set_query_params(
        select_aggregation=select_aggregation
    )

1. Go to view
2. Click on different radio button from Group by group.

Expected behavior:

New value is selected in radio and also changed in query params

Actual behavior:

Nothing happens, at first. Value is changed in radio and also in query params after second click.

Is this a regression?

No

Debug info

• Streamlit version: 0.70.0
• Python version: 3.8.5
• Using pip and venv
• OS version: Mac OS 10.14.6
• Browser version: Chrome 86.0.4240.198 (Official Build) (x86_64)

[tomkomt]

@tybirk-mindway Thank you, that’s perfect. It helped a lot.

I did a few changes to mentioned workaround, because it was failing when app started with empty query params. If default query params were provided, then it worked like a charm.

query_state = st.experimental_get_query_params()
app_state = st.experimental_get_query_params()

session_state = SessionState.get(first_query_params=query_state)
first_query_params = session_state.first_query_params

if len(first_query_params.keys()) == 0:
    session_state.first_query_params = app_state

select_options = ["All", "Case ID", "Cedant", "Doc Type"]
preselected_index = eval(str(first_query_params["select_aggregation"][0])) if "select_aggregation" in app_state else 0
select_aggregation = st.sidebar.radio(
    label="Group by:",
    options=select_options,
    index=preselected_index if preselected_index > -1 else 0,
)

app_state['select_aggregation'] = [select_options.index(select_aggregation)]

st.experimental_set_query_params(**app_state)

So, as was mentioned here, I changed this

first_query_params = session_state.first_query_params
session_state = SessionState.get(first_query_params=query_params)

to this

session_state = SessionState.get(first_query_params=query_state)
first_query_params = session_state.first_query_params

and then I handled default state with empty query params

if len(first_query_params.keys()) == 0:
    session_state.first_query_params = app_state

Then my interpretation of this code

default_index = eval(first_query_params["radio"][0]) if "radio" in app_state else 0

was throwing and error, that arg 1 in eval should be string or etc. Integer was not fine. So I handled it with casting to string:

preselected_index = eval(str(first_query_params["select_aggregation"][0])) if "select_aggregation" in app_state else 0

And the last change. My code inspired by this line:

app_state["radio"] = radio_list.index(genre)

was implemented like this:

app_state['selected_runid'] = [runids_options.index(selected_runid)]

because otherwise state was an integer and not list.

I hope this will help somebody.

[franekp]

@tomkomt @tybirk-mindway @quantoid FYI these problems likely have been solved by the recently-added callbacks functionality in Streamlit. This means that SessionState-based hacks are no longer needed to properly sync input controls with URL query params.

I have made a library of url-aware input controls that automatically sync their state with URL: streamlit-permalink.