task_fraud_detection/src/model_training.py

import pandas as pd
import numpy as np
from sklearn.ensemble import RandomForestClassifier
from sklearn.metrics import classification_report
from sklearn.preprocessing import StandardScaler, OneHotEncoder
from sklearn.compose import ColumnTransformer
from sklearn.pipeline import Pipeline
import joblib
from datetime import datetime


def load_data(train_file, test_file):
    train_df = pd.read_csv(train_file)
    test_df = pd.read_csv(test_file)

    # Drop rows with missing values
    train_df.dropna(inplace=True)
    test_df.dropna(inplace=True)

    return train_df, test_df


def feature_engineering(df):
    # Convert transaction time to datetime
    df['trans_date_trans_time'] = pd.to_datetime(df['trans_date_trans_time'])

    # Extract time features
    df['hour'] = df['trans_date_trans_time'].dt.hour
    df['day_of_week'] = df['trans_date_trans_time'].dt.dayofweek
    df['month'] = df['trans_date_trans_time'].dt.month

    # Calculate age from dob
    df['dob'] = pd.to_datetime(df['dob'])
    df['age'] = (pd.to_datetime('today') - df['dob']).dt.days // 365

    # Calculate distance between user and merchant
    df['distance'] = np.sqrt((df['lat']-df['merch_lat'])**2 + (df['long']-df['merch_long'])**2)

    return df


def train_model(train_df, test_df):
    # Define features and target
    X_train = train_df.drop(['is_fraud', 'trans_date_trans_time', 'trans_num', 'dob', 'unix_time'], axis=1)
    y_train = train_df['is_fraud']

    X_test = test_df.drop(['is_fraud', 'trans_date_trans_time', 'trans_num', 'dob', 'unix_time'], axis=1)
    y_test = test_df['is_fraud']

    # Define preprocessing
    numeric_features = ['amt', 'city_pop', 'hour', 'day_of_week', 'month', 'age', 'distance']
    numeric_transformer = StandardScaler()

    categorical_features = ['category', 'gender', 'job', 'merchant']
    categorical_transformer = OneHotEncoder(handle_unknown='ignore')

    preprocessor = ColumnTransformer(
        transformers=[
            ('num', numeric_transformer, numeric_features),
            ('cat', categorical_transformer, categorical_features)
        ])

    # Create pipeline
    model = Pipeline(steps=[
        ('preprocessor', preprocessor),
        ('classifier', RandomForestClassifier(class_weight='balanced', random_state=42))
    ])

    # Train model
    model.fit(X_train, y_train)

    # Evaluate on test data
    y_pred = model.predict(X_test)
    print("Test Set Performance:")
    print(classification_report(y_test, y_pred))

    return model


def main():
    # Load data
    train_df, test_df = load_data('data/raw/fraudTrain.csv', 'data/raw/fraudTest.csv')

    # Feature engineering
    train_df = feature_engineering(train_df)
    test_df = feature_engineering(test_df)

    # Print dataset sizes after cleaning
    print(f"Training samples after cleaning: {len(train_df)}")
    print(f"Test samples after cleaning: {len(test_df)}")

    # Train model
    model = train_model(train_df, test_df)

    # Save model
    joblib.dump(model, 'models/fraud_model.pkl')
    print("Model saved to models/fraud_model.pkl")

if __name__ == "__main__":
    main()