app.py

import streamlit as st
import math

# App title
st.set_page_config(page_title="Advanced Calculator", page_icon="🧮")
st.title("🧮 Advanced Calculator")
st.write("An advanced calculator with percentage & history")

# Initialize history in session state
if "history" not in st.session_state:
    st.session_state.history = []

# Select operation
operation = st.selectbox(
    "Choose an operation",
    [
        "Addition (+)",
        "Subtraction (-)",
        "Multiplication (*)",
        "Division (/)",
        "Power (x^y)",
        "Modulus (%)",
        "Square Root (√x)",
        "Percentage (x % of y)"
    ]
)

# Inputs
if operation == "Square Root (√x)":
    num = st.number_input("Enter number", value=0.0)

elif operation == "Percentage (x % of y)":
    x = st.number_input("Enter percentage value", value=0.0)
    y = st.number_input("Enter total value", value=0.0)

else:
    num1 = st.number_input("Enter first number", value=0.0)
    num2 = st.number_input("Enter second number", value=0.0)

# Calculate button
if st.button("Calculate"):
    try:
        if operation == "Addition (+)":
            result = num1 + num2
            record = f"{num1} + {num2} = {result}"

        elif operation == "Subtraction (-)":
            result = num1 - num2
            record = f"{num1} - {num2} = {result}"

        elif operation == "Multiplication (*)":
            result = num1 * num2
            record = f"{num1} * {num2} = {result}"

        elif operation == "Division (/)":
            if num2 == 0:
                st.error("Division by zero is not allowed")
                st.stop()
            result = num1 / num2
            record = f"{num1} / {num2} = {result}"

        elif operation == "Power (x^y)":
            result = num1 ** num2
            record = f"{num1} ^ {num2} = {result}"

        elif operation == "Modulus (%)":
            result = num1 % num2
            record = f"{num1} % {num2} = {result}"

        elif operation == "Square Root (√x)":
            if num < 0:
                st.error("Cannot calculate square root of negative number")
                st.stop()
            result = math.sqrt(num)
            record = f"√{num} = {result}"

        elif operation == "Percentage (x % of y)":
            result = (x / 100) * y
            record = f"{x}% of {y} = {result}"

        # Display result
        st.success(f"Result: {result}")

        # Save history
        st.session_state.history.append(record)

    except Exception as e:
        st.error(f"Error: {e}")

# Show history
st.subheader("📜 Calculation History")
if st.session_state.history:
    for h in st.session_state.history:
        st.write(h)
else:
    st.info("No calculations yet")