Show HN: Credkit – Easier Loan Modeling

2 hours ago 1

An open toolbox for credit modeling in Python

Credkit provides elegant, type-safe primitives for building credit models that typically force teams to reach for Excel. From consumer loans to portfolio analytics, credkit offers domain-driven tools designed for precision and composability.

Built for consumer lending (mortgages, auto loans, personal loans) with cash flow modeling, amortization schedules, and present value calculations.

Currently focused on USD-denominated consumer loan products in the US market.

# Using uv (recommended) uv add credkit # Using pip pip install credkit

from credkit import Loan, Money, InterestRate, FlatDiscountCurve from datetime import date # Create a 30-year mortgage loan = Loan.mortgage( principal=Money.from_float(300000.0), annual_rate=InterestRate.from_percent(6.5), term_years=30, origination_date=date(2024, 1, 1), ) # Calculate payment payment = loan.calculate_payment() # ~$1,896.20/month # Generate amortization schedule schedule = loan.generate_schedule() # 720 cash flows (360 principal + 360 interest) # Calculate total interest over life of loan total_interest = loan.total_interest() # Value the loan at market rate market_curve = FlatDiscountCurve( InterestRate.from_percent(5.5), valuation_date=date(2024, 1, 1) ) npv = schedule.present_value(market_curve)

See EXAMPLES.md for more comprehensive examples of all features.

Temporal (credkit.temporal)

Day count conventions: ACT/365, ACT/360, ACT/ACT, 30/360, and more
Periods: Time spans with natural syntax ("30Y", "6M", "90D")
Payment frequencies: Annual, monthly, bi-weekly, etc.
Business day calendars: Holiday-aware date adjustments

Money: Currency-aware amounts with Decimal precision
Interest rates: APR with multiple compounding conventions
Spreads: Basis point adjustments (e.g., "Prime + 250 bps")

Cash Flow (credkit.cashflow)

Cash flows: Individual payment representation with present value
Schedules: Collections with filtering, aggregation, and NPV
Discount curves: Flat and zero curves with interpolation

Loans (credkit.instruments)

Loan types: Mortgages, auto loans, personal loans
Amortization: Level payment, level principal, interest-only, bullet
Schedules: Generate complete payment schedules with principal/interest breakdown
Integration: Full end-to-end from loan creation to NPV calculation

Immutable by default: All core types are frozen dataclasses
Decimal precision: No floating-point errors in financial calculations
Type safety: Full type hints with py.typed marker
Composable: Build complex models from simple primitives
Tested: 148 passing tests with comprehensive coverage

EXAMPLES.md: Comprehensive code examples for all modules

Python 3.13+
No runtime dependencies (uses only standard library)

# Clone and setup git clone https://github.com/jt-hill/credkit.git cd credkit/core-classes uv sync --dev # Run tests uv run pytest tests/ -v # All 148 tests should pass

Contributions welcome! This project follows:

Domain-driven design with immutable primitives
Comprehensive testing

AGPL-3.0

For commercial licensing options, contact the author

148 passing tests covering temporal operations, money arithmetic, cash flow modeling, discount curves, loan instruments, and end-to-end loan valuation.

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