Login Page Creation in Streamlit

Example : A Streamlit program to create a Login Page with Static Validation Value.

import streamlit as st

# Dummy user credentials
users = {
    "admin": "admin123",
    "abc": "abc123",
    "xyz": "xyz123"
}

# Page configuration
st.set_page_config(page_title="Login Page", layout="centered")

# Center the content using columns
col1, col2, col3 = st.columns([1, 2, 1])  # center column is wider

with col2:  # place everything in the center column
    #st.image("https://cdn-icons-png.flaticon.com/512/3064/3064197.png", width=80)
    st.title("🔐 User Login")
    st.subheader("Login to Your Account")

    with st.form("login_form"):
        username = st.text_input("Username", placeholder="Enter your username")
        password = st.text_input("Password", placeholder="Enter your password", type="password")

        col11, col12 = st.columns([1, 3])
        login1 = col11.form_submit_button("Login")
        reset1 = col12.form_submit_button("Reset")

        if login1:
            if not username or not password:
                st.warning("⚠️ Please fill in both username and password.")
            elif username in users and users[username] == password:
                st.success(f"✅ Welcome User, {username}!")
                st.balloons()
            else:
                st.error("❌ Invalid username or password.")

NB: 
(i) The 'unsafe_allow_html=True' tells Streamlit that "Yes, I trust this HTML and want it to be rendered as-is" used in the code.
(ii) Here, "username in users and users[username] == password:"  line is a part of a login check using a dictionary in Python where 'username in users:' is the username entered by the user a key in the users dictionary and 'users[username] == password:' says that the stored password for that username match the password the user typed or not.

Example : A Streamlit program to create a Login Page with Dynamic Validation Value from a MySQL database.

your_project/
│
├── main.py           ← Login page (default starting point)
├── pages/
│   └── dashboard.py  ← Dashboard page (opened after login)

-----------------------  OR  --------------------

main.py (Login Page)

import streamlit as st
from sqlalchemy import create_engine, text

# --- MySQL Connection ---
engine = create_engine("mysql+pymysql://root:@localhost/ejs_forms_db")

# --- Check credentials ---
def validate_login(username, password):
    with engine.connect() as conn:
        result = conn.execute(
            text("SELECT * FROM users WHERE username = :u AND password = :p"),
            {"u": username, "p": password}
        )
        return result.fetchone() is not None

# --- Session state ---
if "logged_in" not in st.session_state:
    st.session_state.logged_in = False

# --- Login Form ---
def login_form():
    st.title("🔐 Login Page")

    username = st.text_input("Username")
    password = st.text_input("Password", type="password")
    login = st.button("Login")

    if login:
        if validate_login(username, password):
            st.session_state.logged_in = True
            st.session_state.username = username  # optional for dashboard
            st.success("✅ Login successful")
            st.switch_page("pages/dashboard.py")  # <-- this will redirect!
        else:
            st.error("❌ Invalid username or password")

# --- Run login ---
login_form()

NB: Here, 'logged_in' is a Boolean flag stored in st.session_state to track whether the user is currently logged in. 
This line ensures that the logged_in session state variable is initialized i.e. -
   - If logged_in = False: the user hasn't logged in yet.
   - If logged_in = True: the user has successfully logged in.
This boolean variable is useful for:-
   - Controlling access to specific parts of the app and,
   - Remembering the user is logged in even if they interact with other pages or rerun the app.

--------------------  OR  ---------------------

dashboard.py (pages/dashboard.py after successfull login)

import streamlit as st

# --- Access Control ---
if "logged_in" not in st.session_state or not st.session_state.logged_in:
    st.error("⛔ Access denied. Please login first.")
    st.stop()

# --- Dashboard UI ---
st.title("📊 Dashboard")
st.success(f"Welcome the logged in user =  {st.session_state.get('username', 'User')}!")

if st.button("Logout"):
    st.session_state.logged_in = False
    st.switch_page("main.py")  # Redirect to login