How to Do Partial Rerun for This Dynamic Form Using Fragments?

TerraX3000 · April 11, 2024, 8:29pm

I’m designing a form which allows users to dynamically add inputs.
The goal is to prevent full script reruns when users add new inputs and enter input values by using the new Streamlit fragments decorator.
However, under some conditions, the full script reruns when the user enters an input value.

This script demonstrates a simplified version of the form.

Each button click adds an expander.
Within the expander, the user enters an input value.
There is a popover and checkbox to allow the user to remove the expander.

To cause the undesired full script rerun:

Add two or more food items
Enter an input value in any input following the first food input
–or–
Use the remove popover on any input following the first food input

The issue appears to only occur when operating on a new input after creating multiple inputs.

I suspect it is related to the limitation that fragments cannot call other fragments.

I wonder if there is a way to structure the code to avoid this issue?

Python v3.10
Streamlit v1.33
GitHub repo: https://github.com/TerraX3000/streamlit_fragment_test
Runs locally

import streamlit as st
import random
import string
from typing import List


def add_food_key_to_session(key):
    print("Running add_food_key_to_session()", key)
    food_input_keys: List = st.session_state["food_input_keys"]
    food_input_keys.append(key)
    st.session_state["food_input_keys"] = food_input_keys


def remove_food_input_key(key):
    print("Running remove_food_input_key()", key)
    food_input_keys: List = st.session_state["food_input_keys"]
    food_input_keys.remove(key)
    st.session_state["food_input_keys"] = food_input_keys


def food_input(key):
    print("Running food_input()", key)
    food = st.text_input("Favorite Food", key=key)
    if food:
        st.write(food)


@st.experimental_fragment()
def add_edit_remove_food_container(key):
    print("Running add_edit_remove_food_container()", key)
    container = st.empty()
    with container.expander("Food Details", expanded=True):
        food_input(key)
        remove_food_popover = st.popover("Remove this food?")
        is_remove_food = remove_food_popover.checkbox(
            "Confirm", key=f"remove-{key}")

        if is_remove_food:
            remove_food_input_key(key)
            container.empty()


def render_food_containers():
    print("Running render_food_containers()")
    food_input_keys: List = st.session_state["food_input_keys"]
    for key in food_input_keys:
        add_edit_remove_food_container(key)


@st.experimental_fragment()
def manage_food_button_and_containers():
    print("Running manage_food_button_and_containers()")
    if st.button("Add Favorite Food"):
        key = get_new_key()
        add_food_key_to_session("food-" + key)
    render_food_containers()
    print("Session State:", st.session_state, "\n")


def get_new_key(k=4):
    key = "".join(random.choices(
        string.ascii_lowercase + string.digits, k=k))
    return key


def run_full_script():
    print("Running run_full_script")
    if "script_run_counter" not in st.session_state:
        st.session_state["script_run_counter"] = 1
    else:
        st.session_state["script_run_counter"] += 1
    if "food_input_keys" not in st.session_state:
        st.session_state["food_input_keys"] = []

    stats_container = st.container()
    st.divider()

    if st.button("Reset Counter"):
        st.session_state["script_run_counter"] = 1
    if st.button("Reset form"):
        for key in st.session_state.keys():
            del st.session_state[key]
        st.session_state["script_run_counter"] = 1
        st.session_state["food_input_keys"] = []

    manage_food_button_and_containers()
    with stats_container:
        if st.session_state["script_run_counter"] > 1:
            st.title(":red[Full Script Run -- You Lose!]")
            print("\n", "Full Script Run -- You Lose!", "\n")
        st.write(
            f'#### Full Script Run Counter: {st.session_state["script_run_counter"]}')
        st.write(
            "Goal: allow users to dynamically add/edit/delete food inputs without a full script rerun.")
    st.divider()
    with st.expander("Session State", expanded=False):
        st.json(st.session_state)


run_full_script()

ferdy · April 25, 2024, 1:41pm

The main function run_full_script is huge, it calls a fragment-decorated function and there are other functions that are not fragment-decorated. So whenever there are changes in the states, expects a full rerun to trigger.

TerraX3000 · August 21, 2024, 10:26pm

TL;DR: Streamlit version 1.37 supports nested fragments and that update appears to resolve the issue I was having.

Updated code below replaces st.experimental_fragment with st.fragment.

I am unable to cause a full script rerun doing any of the actions I listed in my original post.

This is really cool!!!

import streamlit as st
import random
import string
from typing import List


def add_food_key_to_session(key):
    print("Running add_food_key_to_session()", key)
    food_input_keys: List = st.session_state["food_input_keys"]
    food_input_keys.append(key)
    st.session_state["food_input_keys"] = food_input_keys


def remove_food_input_key(key):
    print("Running remove_food_input_key()", key)
    food_input_keys: List = st.session_state["food_input_keys"]
    food_input_keys.remove(key)
    st.session_state["food_input_keys"] = food_input_keys


def food_input(key):
    print("Running food_input()", key)
    food = st.text_input("Favorite Food", key=key)
    if food:
        st.write(food)


@st.fragment()
def add_edit_remove_food_container(key):
    print("Running add_edit_remove_food_container()", key)
    container = st.empty()
    with container.expander("Food Details", expanded=True):
        food_input(key)
        remove_food_popover = st.popover("Remove this food?")
        is_remove_food = remove_food_popover.checkbox(
            "Confirm", key=f"remove-{key}")

        if is_remove_food:
            remove_food_input_key(key)
            container.empty()


def render_food_containers():
    print("Running render_food_containers()")
    food_input_keys: List = st.session_state["food_input_keys"]
    for key in food_input_keys:
        add_edit_remove_food_container(key)


@st.fragment()
def manage_food_button_and_containers():
    print("Running manage_food_button_and_containers()")
    if st.button("Add Favorite Food"):
        key = get_new_key()
        add_food_key_to_session("food-" + key)
    render_food_containers()
    print("Session State:", st.session_state, "\n")


def get_new_key(k=4):
    key = "".join(random.choices(
        string.ascii_lowercase + string.digits, k=k))
    return key


def run_full_script():
    print("Running run_full_script")
    if "script_run_counter" not in st.session_state:
        st.session_state["script_run_counter"] = 1
    else:
        st.session_state["script_run_counter"] += 1
    if "food_input_keys" not in st.session_state:
        st.session_state["food_input_keys"] = []

    stats_container = st.container()
    st.divider()

    if st.button("Reset Counter"):
        st.session_state["script_run_counter"] = 1
    if st.button("Reset form"):
        for key in st.session_state.keys():
            del st.session_state[key]
        st.session_state["script_run_counter"] = 1
        st.session_state["food_input_keys"] = []

    manage_food_button_and_containers()
    with stats_container:
        if st.session_state["script_run_counter"] > 1:
            st.title(":red[Full Script Run -- You Lose!]")
            print("\n", "Full Script Run -- You Lose!", "\n")
        st.write(
            f'#### Full Script Run Counter: {st.session_state["script_run_counter"]}')
        st.write(
            "Goal: allow users to dynamically add/edit/delete food inputs without a full script rerun.")
    st.divider()
    with st.expander("Session State", expanded=False):
        st.json(st.session_state)


run_full_script()

TerraX3000 · August 22, 2024, 3:13pm

Update: Although Streamlit v.137 allows nested fragments, I discovered a bug where Streamlit will incorrectly rerender an element previously created and removed with st.empty.

Steps to Reproduce:

Click Add Favorite Food
Type pizza
Click Remove this food and confirm
Click Add Favorite Food
Type ice cream

During step 5, ice cream will be replaced with pizza and an error will be displayed.

To aid troubleshooting, I’ve added the input key value to the form. Note that the key value reverts to the initial key value when the error occurs. This suggests that Streamlit is maintaining the previous container in memory and redrawing it.

Error When Removing Container

Updated code:

import streamlit as st
import random
import string
from typing import List


def add_food_key_to_session(key):
    print("Running add_food_key_to_session()", key)
    food_input_keys: List = st.session_state["food_input_keys"]
    food_input_keys.append(key)
    st.session_state["food_input_keys"] = food_input_keys


def remove_food_input_key(key):
    print("Running remove_food_input_key()", key)
    food_input_keys: List = st.session_state["food_input_keys"]
    print("Before Remove: Session State:", st.session_state, "\n")
    food_input_keys.remove(key)
    st.session_state["food_input_keys"] = food_input_keys
    print("After Remove: Session State:", st.session_state, "\n\n\n\n")


def food_input(key):
    print("Running food_input()", key)
    food = st.text_input(f"Favorite Food ({key})", key=key)
    if food:
        st.write(food)


@st.fragment()
def add_edit_remove_food_container(key):
    print("Running add_edit_remove_food_container()", key)
    container = st.empty()
    with container.expander("Food Details", expanded=True):
        food_input(key)
        remove_food_popover = st.popover(
            f"Remove this food? ({key})")
        is_remove_food = remove_food_popover.checkbox(
            "Confirm", key=f"remove-{key}")

        if is_remove_food:
            remove_food_input_key(key)
            container.empty()


def render_food_containers():
    print("Running render_food_containers()")
    food_input_keys: List = st.session_state["food_input_keys"]
    for key in food_input_keys:
        add_edit_remove_food_container(key)


@st.fragment()
def manage_food_button_and_containers():
    print("Running manage_food_button_and_containers()")
    if st.button("Add Favorite Food"):
        key = get_new_key()
        add_food_key_to_session("food-" + key)
    render_food_containers()
    print("Session State:", st.session_state, "\n\n\n\n")


def get_new_key(k=4):
    key = "".join(random.choices(
        string.ascii_lowercase + string.digits, k=k))
    return key


def run_full_script():
    print("Running run_full_script")
    if "script_run_counter" not in st.session_state:
        st.session_state["script_run_counter"] = 1
    else:
        st.session_state["script_run_counter"] += 1
    if "food_input_keys" not in st.session_state:
        st.session_state["food_input_keys"] = []

    stats_container = st.container()
    st.divider()

    if st.button("Reset Counter"):
        st.session_state["script_run_counter"] = 1
    if st.button("Reset form"):
        for key in st.session_state.keys():
            del st.session_state[key]
        st.session_state["script_run_counter"] = 1
        st.session_state["food_input_keys"] = []

    manage_food_button_and_containers()
    with stats_container:
        if st.session_state["script_run_counter"] > 1:
            st.title(":red[Full Script Run -- You Lose!]")
            print("\n", "Full Script Run -- You Lose!", "\n")
        st.write(
            f'#### Full Script Run Counter: {st.session_state["script_run_counter"]}')
        st.write(
            "Goal: allow users to dynamically add/edit/delete food inputs without a full script rerun.")
    st.divider()
    with st.expander("Session State", expanded=False):
        st.json(st.session_state)


run_full_script()

TerraX3000 · August 22, 2024, 5:31pm

Discovered GitHub issue opened for this issue here:

github.com/streamlit/streamlit

Interacting with widgets inside st.fragment functions can lead to the wrong fragment instance been shown. This used to work in v1.36

opened 04:18PM - 20 Aug 24 UTC

flucas96

type:bug status:confirmed priority:P2 feature:st.fragment

### Checklist - [X] I have searched the [existing issues](https://github.com/…streamlit/streamlit/issues) for similar issues. - [X] I added a very descriptive title to this issue. - [X] I have provided sufficient information below to help reproduce this issue. ### Summary Hi, sorry for the somewhat unclear title. I hope my example makes the issues clearer. Starting in version 1.37.1 changing a value in a function decorated with @st.fragment might lead to displaying the wrong fragment. This happens if there once where multiple fragments instances of the same function created ### Reproducible Code Example [![Open in Streamlit Cloud](https://static.streamlit.io/badges/streamlit_badge_black_white.svg)](https://issues.streamlitapp.com/?issue=gh-9313) ```Python import streamlit as st import pandas as pd #Dummy data # from dummy_data import get_analysis, Analysis from packaging import version from typing import Literal class Analysis(): """ Dummy class to represent an analysis. In reality, this is a SQLAlchemy Model """ def __init__(self, id, name, type: Literal["line", "bar"]): self.id = id self.name = name self.type = type #Some dummies dummy_analysis1 = Analysis(1, "dummy1", "line") dummy_analysis2 = Analysis(2, "dummy2", "bar") dummy_analysis3 = Analysis(3, "dummy3", "line") dummy_analysis4 = Analysis(4, "dummy4", "bar") @st.cache_data() def get_analysis() -> Analysis: """ Dummy function to get an analysis object. """ return [dummy_analysis1, dummy_analysis2, dummy_analysis3, dummy_analysis4] if version.parse(st.__version__) >= version.parse("1.37.0"): fragment_handler = st.fragment else: fragment_handler = st.experimental_fragment def class_to_dataframe(objects): """ Converts a list of class instances to a pandas DataFrame. Parameters: objects (list): A list of class instances. Returns: pandas.DataFrame: A DataFrame where each row represents an instance and each column an attribute of the class. """ # Extract attribute dictionaries from objects using vars() or obj.__dict__ data = [vars(obj) for obj in objects] # Create and return the DataFrame return pd.DataFrame(data).drop(columns=["_sa_instance_state"], errors="ignore") def _get_selected_analysis(df: pd.DataFrame, analysis: list[Analysis]): """ Updates the session state with the selected analysis. Parameters: df (pd.DataFrame): DataFrame containing the analysis data. analysis (list[Analysis]): List of analysis objects. """ selected_ausw = df.loc[df["selector"] == True]["id"].to_list() st.session_state["selected_analysis"] = [ ausw for ausw in analysis if ausw.id in selected_ausw ] @fragment_handler def list_analysis(analysis: list[Analysis]): """ Creates a list of all available analysis.# Parameters: analysis (Analysis): The analysis object to be displayed. """ if "selected_analysis" not in st.session_state: st.session_state["selected_analysis"] = [] df_raw = class_to_dataframe(analysis) if "selected_analysis" in st.session_state: df_raw.loc[ df_raw["id"].isin( [ausw.id for ausw in st.session_state["selected_analysis"]] ), "selector", ] = True column_config = { "selector": st.column_config.CheckboxColumn( "Select", default=False ), "name": st.column_config.TextColumn("Name", disabled=True), "type": st.column_config.TextColumn("Type", disabled=True), } column_order = ("selector", "name", "type") st.subheader("Choose your Analysis") res = st.data_editor( df_raw, column_config=column_config, column_order=column_order, hide_index=True, key="analysis_table", use_container_width=True, ) selected_auswertungen = res.loc[res["selector"] == True]["id"].to_list() disabled = False if len(selected_auswertungen) > 0 else True # disabled = False # Buttons col_btn_show, _, col_btn_del = st.columns([1, 0.1, 1]) with col_btn_show: if st.button( "**Show**", use_container_width=True, disabled=disabled, key="show_analysis_button", ): _get_selected_analysis(res, analysis) st.rerun() @fragment_handler def show_selected_analysis(analysis: Analysis): st.subheader(f"Selected Analysis: {analysis.name}") st.write("ID: ", analysis.id) st.write("**Some Random Input: Select a value to multiple the ID by**") multipe = st.slider("Multiply by", 1, 10, 1,key=f"slider_{analysis.id}") st.write("New ID: ", analysis.id * multipe) #Here we create the dashboard page: st.session_state["selected_analysis"] = st.session_state.get("selected_analysis", []) #display the list of analysis list_analysis(analysis=get_analysis()) if "selected_analysis" in st.session_state: #display the selected analysis if len(st.session_state["selected_analysis"]) > 0: for analysis in st.session_state["selected_analysis"]: show_selected_analysis(analysis) st.divider() with st.sidebar: with st.container(border=True): st.write("**What is the bug**") st.write("""Starting in **version 1.37.1** changing a value in a function decorated with `@st.fragment`might lead to displaying the wrong fragment. This happens if there once where multiple fragments instances of the same function created """) st.write("**How to reproduce**") st.write("""1. Install Streamlit Version 1.37.1\n\n2. Select the first two analysis options and click on the **Show** button \n\n3. Play around with the two sliders and see that everything works as expected.\n\n4. Now deselect the first analysis and keep the second analysis selected\n\n5. Click on the **Show** button.\n\n6. Only the second analysis is now being displayed. Until here everything was working as expected.\n\n7. If you know touch the slider again, suddently the first analysis is being displayed again instead of the second one. \n\n """) st.write("**Excepted behavior**") st.write("""The expected behavior can be observed by installing Streamlit Version 1.36""") st.write("When this older version is installed, touching the slider will not change the displayed analysis.") ``` ### Steps To Reproduce 1. Install Streamlit Version 1.37.1 2. Select the first two analysis options and click on the Show button 3. Play around with the two sliders and see that everything works as expected. 4. Now deselect the first analysis and keep the second analysis selected 5. Click on the Show button. 6. Only the second analysis is now being displayed. Until here everything was working as expected. 7. If you know touch the slider again, suddently the first analysis is being displayed again instead of the second one. 8. Now install Streamlit Version 1.36 and do the same again to see the expected behavior. ### Expected Behavior I would expect the content shown the be the same. ### Current Behavior The shown content switches bag to the previously selected value that was rendered in the fragment. ### Is this a regression? - [X] Yes, this used to work in a previous version. ### Debug info - Streamlit version: 1.37.1 / 1.36 - Python version: 3.9 - Operating System: Windows & Linux - Browser: Chrome & Edge ### Additional Information _No response_

It appears the bug was introduced in v1.37.

TerraX3000 · August 31, 2024, 11:40am

The bug was resolved and fixed in Streamlit v.1.38. The script now runs without error and we call this issue Solved! Thanks, Streamlit Team!

system · September 2, 2024, 11:40am

This topic was automatically closed 2 days after the last reply. New replies are no longer allowed.

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How to Do Partial Rerun for This Dynamic Form Using Fragments?

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