Session State

if "counter" not in st.session_state:
    st.session_state.counter = 0

# Read
current_val = st.session_state.counter

# Write / Update
st.session_state.counter += 1

import streamlit as st

st.set_page_config(page_title="Student Log", layout="centered")

st.title("🎓 Student Performance Logger")
st.write("This app uses Session State to keep track of added students without losing data on reruns.")

# 1. Initialize session state list if it doesn't exist
if "student_logs" not in st.session_state:
    st.session_state.student_logs = []

# Form to input student details
with st.form("student_form", clear_on_submit=True):
    name = st.text_input("Student Name")
    score = st.slider("Exam Score", 0, 100, 75)
    submit = st.form_submit_button("Add Student")
    
    if submit:
        if name.strip() != "":
            # 2. Append new student log to session state list
            st.session_state.student_logs.append({"name": name, "score": score})
            st.success(f"Added {name}!")
        else:
            st.error("Please enter a name.")

st.divider()

# Display log from session state
st.subheader("📋 Logged Student Records")
if len(st.session_state.student_logs) > 0:
    for idx, student in enumerate(st.session_state.student_logs):
        st.write(f"{idx + 1}. **{student['name']}** — Score: {student['score']}%")
    
    # 3. Clear button to empty the session state list
    if st.button("Clear Log"):
        st.session_state.student_logs = []
        st.rerun() # Forces a rerun to update the UI immediately
else:
    st.info("No students logged yet.")

streamlit run exercise_session_state.py