Programatically setting widget values and bookmarking app state

Show the Community!
1

Hi all,

I ran into some trouble with getting and setting query parameters yesterday, but found a solution which I would like to share. It relies on a few of the well-known hacks, and allows the definition of predefined states accessible by the push of a button. In addition, it showcases how the experimental get and set query parameters can be used, inspired by this comment. Hope the snippet is useful for some people :slight_smile:

import streamlit as st
import session_state
from streamlit.script_runner import RerunException
from streamlit.script_request_queue import RerunData

query_params = st.experimental_get_query_params()

state = session_state.get(
    session_id=0, first_query_params=st.experimental_get_query_params()
)
first_query_params = state.first_query_params

default_values = {
    "my_checkbox": int(state.first_query_params.get("my_checkbox", [0])[0]),
    "my_radio_button": int(state.first_query_params.get("my_radio_button", [2])[0]),
    "my_slider": int(state.first_query_params.get("my_slider", [1])[0]),
    "my_slider_with_two_values": (
        int(state.first_query_params.get("my_slider_with_two_values_min", [5])[0]),
        int(state.first_query_params.get("my_slider_with_two_values_max", [100])[0]),
    ),
    "my_multiselect": state.first_query_params.get("my_multiselect", ["Option 1"]),
}

my_checkbox = st.checkbox(
    "Tick me!", key=state.session_id, value=default_values["my_checkbox"]
)
query_params["my_checkbox"] = int(my_checkbox)

my_radio_options = ["Eat", "Sleep", "Both"]

my_radio_button = st.radio(
    "Options",
    my_radio_options,
    key=state.session_id,
    index=default_values["my_radio_button"],
)
query_params["my_radio_button"] = my_radio_options.index(my_radio_button)

my_slider = st.slider(
    "Slider",
    min_value=0,
    max_value=200,
    key=state.session_id,
    value=default_values["my_slider"],
)
query_params["my_slider"] = my_slider

my_slider_with_two_values = st.slider(
    "Slider with two values",
    min_value=0,
    max_value=100,
    key=state.session_id,
    value=default_values["my_slider_with_two_values"],
)
query_params["my_slider_with_two_values_min"] = my_slider_with_two_values[0]
query_params["my_slider_with_two_values_max"] = my_slider_with_two_values[1]

my_multiselect = st.multiselect(
    "Select options!",
    ["Option 1", "Option 2", "Option 3"],
    key=state.session_id,
    default=default_values["my_multiselect"],
)
query_params["my_multiselect"] = my_multiselect

if st.sidebar.button("Set predefined filtering"):
    state.first_query_params = dict(
        my_checkbox=[1],
        my_radio_button=[0],
        my_slider_with_two_values_min=[15],
        my_multiselect=["Option 2"],
    )
    state.session_id += 1
    raise RerunException(RerunData())

st.experimental_set_query_params(**query_params)
7 Likes
2

Hey can you please explain what RerunException(RerunData()) is using and when I do just st.experimental_rerun() , for some reason the queryparam dictionary is becoming {} , can you please help me

3

My requirement is when the user click some button , I should update the query parameters and rerun the script from start using the updated query param list

4

Hi Meesa, welcome to the community!

Could you share some sample code, perhaps that makes it easier to help? :slight_smile: I think the code above should be able to meet your requirements, but perhaps it needs some small adjustments.

I do not think there is a difference between RerunException(RerunData()) and st.experimental_rerun(), you can see in the streamlit source code that experimental rerun is just a prettier wrapper of the same code.

Best,
Peter

5

Hi Peter,

I figured out the solution with the help of your code, I have a doubt regarding scalability of solution like.,as we are keeping key= session_id and session_id being incremented when user clicks some button , so now number of keys just keep on growing and will we be running into some performance issues?

6

Hi Meesa,

Good question! Iā€™m not sure how Streamlit handles it internally when new keys are generated and the old widgets are no longer used. Iā€™ve not experienced problems thus far, but it may be a good idea to do some kind of testing on thisā€¦ Sorry to not be of more help.

Best,
Peter

7

Yeah Peter when new widgets are been used streamlit is removing old ones , so instead of incrementing session id I am making it 0,1 alternatively and itā€™s working fine.

thanks,
Shivaram

8

Hi Peter ,

this state variable is getting shared across two different application instances , I tried running my app in two different tabs of my machine and the state variable is behaving as a common variable to both the tabs like itā€™s getting overwritten by other tabs .

Let say I incremented state.id in 1 tab , the change is getting reflected in other tab , Can you suggest me a way to keep this state variable as local to particular user .

My use case is I want my app to be used by multiple users at same time.

thanks,
Shivaram

9

Hi Shivaram,

I think the state will not be shared if you e.g. use different browsers or different machines. So it should be possible for several users to use the app at a time as long as theyā€™re not all using the same machine :slight_smile:

10

Hey Peter ,

So I found a solution for this

import streamlit.report_thread as ReportThread
from streamlit.server.server import Server


class SessionState(object):
    def __init__(self, **kwargs):
        for key, val in kwargs.items():
            setattr(self, key, val)


def get(**kwargs):

    ctx = ReportThread.get_report_ctx()
    current_server = Server.get_current()

    if not hasattr(current_server, 'my_state'):
        current_server.my_state = {}

    if str(ctx.session_id) not in current_server.my_state.keys():
        current_server.my_state[str(ctx.session_id)] = SessionState(**kwargs)

    return current_server.my_state[str(ctx.session_id)]

So when I am creating from different browsers I am getting different ctx.session_id , and as current_server is fixed for this Server , so I just added a new attribute my state which is a dictionary with keys as ctx.session_id and values are the state objects , so by this code I can keep different states for different browsers , itā€™s working though , is this correct way of doing things or will I get issues in future?

11

Hi Shivaram,

If it seems to be working for you, I guess it is ok. To be honest, I donā€™t think Iā€™m the right person to answer thisā€¦
What I can say though, is that Streamlit are quite soon releasing integrated session_state so we do not have to rely on this ā€˜hackā€™ with the session_state.py file anymore and I think it will be beneficial to switch to this official implementation once it is released. With this, there are also possibilities to provide widget callbacks which I think will be very handy for managing query parameters. Iā€™m not employed by Streamlit, so I cannot give a timeline on when its out, but looking at the heavy activity in the PRs I assume it will be released within a month or two.

12

Is there any hack to synchronize multiple people writing into same file in streamlit , I want to do some thing like lock() unlock() before everythread accessing the shared resource so that one thread waits for the other.

13

Iā€™m not sure - it sounds like it will be a bit difficult, but I can see you made another thread, lets hope someone can help you there. My intuition would say that you probably need to write to a database instead, but I do not know the usecase.

14

Hey can u see my solution on other thread? I feel itā€™s correct only!!

15

@PeterT @Meesa_Shivaram_Prasa I made a library of url-aware widgets that gives you the ā€œbookmarking app stateā€ functionality for free: streamlit-permalink