model_utils.py

import pickle
import pandas as pd
import numpy as np
import streamlit as st
import io

def load_model(uploaded_file):
    """
    Load an uploaded model file
    
    Args:
        uploaded_file: Streamlit UploadedFile object containing the model
        
    Returns:
        The loaded model object
    """
    try:
        # Read the file
        bytes_data = uploaded_file.getvalue()
        
        # Load the model
        model = pickle.loads(bytes_data)
        return model
    except Exception as e:
        raise ValueError(f"Failed to load model: {str(e)}")

def predict_price(model, input_df, with_confidence_interval=False, confidence_level=0.95, error_margin=0.15):
    """
    Make prediction using the loaded model with optional confidence interval
    
    Args:
        model: The loaded XGBoost model
        input_df (pd.DataFrame): Processed input dataframe
        with_confidence_interval (bool): Whether to return confidence interval
        confidence_level (float): Confidence level (between 0 and 1)
        error_margin (float): Estimated error margin as a proportion of the prediction
        
    Returns:
        If with_confidence_interval is False:
            float: Predicted price
        If with_confidence_interval is True:
            tuple: (predicted_price, lower_bound, upper_bound)
    """
    try:
        # Make prediction
        prediction = model.predict(input_df)
        predicted_price = float(prediction[0])
        
        if with_confidence_interval:
            # Map confidence levels to z-scores
            z_scores = {
                0.50: 0.674,
                0.80: 1.282,
                0.90: 1.645,
                0.95: 1.96,
                0.99: 2.576,
                0.999: 3.291
            }
            
            # Get the appropriate z-score (default to 95% if not found)
            z_score = z_scores.get(confidence_level, 1.96)
            
            # Calculate the margin of error
            margin = predicted_price * error_margin
            
            # Calculate the bounds of the confidence interval
            lower_bound = max(0, predicted_price - (z_score * margin))
            upper_bound = predicted_price + (z_score * margin)
            
            return predicted_price, lower_bound, upper_bound
        else:
            return predicted_price
    except Exception as e:
        raise ValueError(f"Failed to make prediction: {str(e)}")