Streamlit: Manually setting Selectbox and Date_Input to values

Question

I'm building an app that, on default, sets date_input and selectbox options

dateoption = st.sidebar.date_input("Select Date", value=get_previous_business_day(dt.date.today()))
nameoption = st.sidebar.selectbox(f"Select from {name_count} names", individual_names.NAME.values.tolist(), index=None, placeholder="Name")

The user can manually select a date and a name from the options.

I now have added functionality where the app's link can be embedded with parameters, so the dateoption and nameoption can be prefilled. However, I am struggling with how I can force select the two variables. This is what I'm trying:

params = st.query_params.to_dict()

if 'name' in params:
    nameoption = params['name']
    # This did not work, and I also tried selecting the value of the index to place as the option but that just created another nameoption selectbox right below the actual one
    #st.session_state.nameoption = individual_names.NAME.values.tolist().index(params['name'])
if 'date' in params:
    # This doesn't change the selection
    dateoption = datetime.strptime(params['date'], '%Y%m%d').date()

How can I set the nameoption and dateoption fields equal to what the parameters state?

EDIT: A few of you were asking about some working code, please see below:

This is the initialized code:

import datetime
import streamlit as st

dateoption = st.sidebar.date_input("Select Date", value=datetime.date(2019, 7, 6))
nameoption = st.sidebar.selectbox(f"Select from {name_count} names", ['Mary','Beth','Sue','Bob'], index=None, placeholder="Name")

Now let's say that, in my app URL, I add name and date parameters: https://myworkingapp.com:40001/?name=Sue&date=20250501

This can be retrieved by fetching the params variable, which is in the form of a dictionary: params: {'name': 'Sue, 'date': '20250501'}

My question is how can I set the nameoption and dateoption variables to those values from the params dictionary. I tried setting them below, but that didn't work:

params = st.query_params.to_dict()

if 'name' in params:
    nameoption = params['name']
    # This did not work, and I also tried the line below selecting the value of the index to place as the option but that just created another nameoption selectbox right below the actual one
    #st.session_state.nameoption = individual_names.NAME.values.tolist().index(params['name'])
if 'date' in params:
    # This doesn't change the selection
    dateoption = datetime.strptime(params['date'], '%Y%m%d').date()

Please clarify your problem, currently, it is very hard to understand what the problem is. — Aadvik
– Aadvik, Commented Aug 26 at 18:04
How can I set the nameoption and dateoption fields equal to what the parameters state? — mmv456
– mmv456, Commented Aug 26 at 18:07
I don't now if I understand problem but if you want to change value inside widget then you have to filter data before creating widget and assign new value when you create widget. — furas
– furas, Commented Aug 26 at 20:03
better create minimal working code which we could test. And you have to better descrive what you want to get. — furas
– furas, Commented Aug 26 at 20:04

furas · Accepted Answer · 2025-08-27 14:18:14Z

Frankly, I don't know if I understand what you want to do but I would do:

It displays widgets with parameters from url (query_params)
and it also assigns values to variables nameoptions, dateoption

import datetime
import streamlit as st

params = st.query_params.to_dict()

# ---

all_names = ['Mary','Beth','Sue','Bob']

if 'name' in params and params['name'] in all_names:
    param_index = all_names.index(params['name'])
else:
    param_index = None

nameoption = st.sidebar.selectbox(f"Select from {len(all_names)} names", all_names, index=param_index, placeholder="Name")

# ---

if 'date' in params:
    try:
        param_date = datetime.datetime.strptime(params['date'], '%Y%m%d').date()
    except Exception as ex:  # if `date` has wrong format`
        print(f"{ex = }")
        param_date = datetime.date(2019, 7, 6)
else:
    param_date = datetime.date(2019, 7, 6)

dateoption = st.sidebar.date_input("Select Date", value=param_date)

# ---

st.text(F"name: {nameoption}, date: {dateoption}")

EDIT:

Similar code using only try/except

import datetime
import streamlit as st

params = st.query_params.to_dict()

# ---

all_names = ['Mary','Beth','Sue','Bob']

try:
    param_index = all_names.index(params['name'])
except Exception as ex:
    print(f"{ex = }")
    param_index = None

nameoption = st.sidebar.selectbox(f"Select from {len(all_names)} names", all_names, index=param_index, placeholder="Name")

# ---

try:
    param_date = datetime.datetime.strptime(params['date'], '%Y%m%d').date()
except Exception as ex:
    print(f"{ex = }")
    param_date = datetime.date(2019, 7, 6)

dateoption = st.sidebar.date_input("Select Date", value=param_date)

# ---

st.text(F"name: {nameoption}, date: {dateoption}")

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