Hands-On Project: Credit Score Prediction Using Machine Learning with Python and Scikit-Learn

This project provides a detailed guide on building credit score prediction models using decision tree and random forest algorithms, covering the complete machine learning workflow including data preprocessing, feature engineering, model training, and evaluation. The goal is to build an end-to-end system to help understand the application of classification algorithms in financial risk control scenarios and enhance relevant technical and business understanding.

Credit scoring is a core decision-making tool in the financial sector. Traditional methods rely on simple rules or statistical models, while machine learning brings new possibilities. The objective of this project is to build an end-to-end machine learning system that predicts credit score levels based on customers' financial information and behavioral data, and to deeply understand the application of decision trees and random forests in financial risk control.

Data Source and Composition

The project uses two datasets: clientes.csv (historical customer information for training) and novos_clientes.csv (new customer data for prediction).

Key Feature Types

• Demographic features: Age, occupation, education level, etc. (note legal/ethical constraints);
• Financial behavior features: Income, savings, repayment records, number of overdue instances, debt level, etc.;
• Credit history features: Number of credit accounts, usage years, query frequency, past loan records, etc.

Missing Value Handling

• Numeric: Median/mean filling or predictive filling;
• Categorical: Mode filling or "Unknown" category;
• Delete: Directly remove features/samples with excessively high missing ratios.

Categorical Variable Encoding

• Label encoding: Suitable for ordinal categories;
• One-hot encoding: Suitable for nominal categories;
• Target encoding: Suitable for high-cardinality categories.

Feature Scaling

Although decision trees/random forests are not sensitive to scale, unified scaling helps with numerical stability, feature importance comparison, and subsequent integration.

Decision Tree Model

• Splitting criteria: Gini impurity, information gain, optimal split point selection;
• Pruning strategies: Max depth, minimum samples per leaf, minimum split gain (to prevent overfitting).

Random Forest Model

• Bagging mechanism: Bootstrap sampling, random feature selection, voting integration;
• Advantages: Reduce overfitting, improve stability, provide feature importance, support parallel training.

Model Evaluation Metrics

• Accuracy: Initial reference, may be misleading for imbalanced classes;
• Precision/Recall/F1: Measure classification performance;
• ROC curve and AUC: Robust for imbalanced problems, measure discrimination ability.

Model Comparison

• Training set: Decision tree has high accuracy but is prone to overfitting;
• Test set: Random forest has better generalization ability;
• Stability: Random forest is more robust;
• Interpretability: Decision tree is easier to understand.

Feature Importance

• Calculation methods: Impurity reduction (simple but biased for high cardinality), permutation importance (robust but high cost);
• Business insights: Identify key drivers, risk indicators, and guide data collection.

New Client Scoring Process

1. Data validation → 2. Feature engineering (same as training preprocessing) →3. Model inference →4. Result explanation (confidence + key factors).

Model Deployment Considerations

• Persistence: Save models with joblib/pickle;
• API encapsulation: RESTful interface for calls;
• Monitoring and update: Regular performance evaluation, retrain if necessary;
• Compliance: Meet financial regulatory requirements.

Learning Value

• Technical: Data preprocessing, model training/evaluation, result interpretation;
• Business: Credit risk concepts, financial data characteristics, ethics of model application.

Extension and Improvement

• Algorithms: Try XGBoost/LightGBM, deep learning, imbalance handling (SMOTE etc.);
• Feature engineering: Feature crossing, time features, external data integration;
• Model interpretation: SHAP values, LIME, rule extraction.

Conclusion

Credit scoring is a classic machine learning application in finance. This project covers core skills (data processing, model training, etc.) which are basic for data scientists. You can further explore complex algorithms and feature engineering to build more accurate and robust systems.