app.py

import streamlit as st
import re

def calculate(value, operation):
    """
    Perform the specified operation on the given value.

    Parameters:
    value (int or float): The number to operate on.
    operation (str): The operation to perform ('square', 'cube', 'double').

    Returns:
    int or float: The result of the operation.
    """
    operations = {
        'square': lambda x: x ** 2,
        'cube': lambda x: x ** 3,
        'double': lambda x: x * 2
    }
    return operations[operation](value)

def is_valid_input(user_input):
    """
    Validate user input using regular expressions to ensure it is a number.

    Parameters:
    user_input (str): The user input to validate.

    Returns:
    bool: True if the input is valid, False otherwise.
    """
    pattern = r'^\d+(\.\d+)?$'  # Match integers and floating point numbers
    return bool(re.match(pattern, user_input))

def main():
    """
    The main function to run the Streamlit app.
    """
    st.title("Enhanced Calculator")

    # Select operation
    operation = st.selectbox("Select an operation", ('square', 'cube', 'double'))

    # Slider for numeric input
    x = st.slider('Select a value', min_value=0.0, max_value=100.0, value=1.0, step=0.1)
    
    # Validate numeric input using regular expression
    user_input = st.text_input("Or enter a number:")
    if user_input and is_valid_input(user_input):
        x = float(user_input)
    elif user_input:
        st.error("Invalid input. Please enter a valid number.")

    # Calculate the result
    result = calculate(x, operation)
    
    # Display the result
    st.write(f'The {operation} of {x} is {result}')

if __name__ == "__main__":
    main()