Streamlit button example

button_example.md

Example for discussion: https://discuss.streamlit.io/t/how-to-evolve-complex-state-e-g-annotate-data/

Install the requirements.

fastapi==0.42.0
streamlit==0.49.0
uvicorn==0.9.1

Run the server.

uvicorn server:app --reload

Run Streamlit.

streamlit run letters.py

letters.py

import streamlit as st
import requests

st.subheader('existing letters')
letters = requests.get('http://127.0.0.1:8000/letters').json()
for letter in letters:
    st.write(letter)

st.subheader('add new letters')
new_candidates = []
for new_letter in ['d', 'e', 'f']:
    st.write(f'add {new_letter}')
    add_letter = st.checkbox(f'add {new_letter}')
    if add_letter:
        new_candidates.append(new_letter)

submit = st.button('submit new letters')
if submit:
    requests.post('http://127.0.0.1:8000/letters', json=new_candidates)

server.py

from fastapi import FastAPI
from typing import List

app = FastAPI()

LETTERS = []


@app.get("/letters")
def list_letters():
    return LETTERS


@app.post("/letters")
def add_letters(letters: List[str]):
    LETTERS.extend(letters)
    return {'added': len(letters)}