MoneyWarp
Bend time. Model cash.
Development Stage Notice -- MoneyWarp is in active development (alpha). Core classes are stable and covered by 5700+ tests, but the API may evolve.
MoneyWarp is a Python library for working with the time value of money. It treats loans, annuities, and investments as cash flows through time -- and gives you the tools to warp them back and forth between present, future, and everything in between.
Features
- Time Machine (Warp) -- travel to any date and see loan state as of that moment
- PMT, NPV, IRR, MIRR -- core finance functions powered by scipy
- Loan tracking -- payments, fines, mora interest, grace periods
- High-precision Money -- Decimal arithmetic, never floats
- Amortization schedules -- French (Price) and SAC (Inverted Price)
- Flexible dates -- irregular due dates, smart month-end handling
- Type-safe interest rates -- explicit percentage handling, frequency conversions
- Percentage type -- non-temporal flat percentages for fees, fines, MDR
- Installments and Settlements -- first-class repayment plan and payment allocation
- Payment waivers -- waive fines, mora, or overdue interest per payment
- Working day calendars -- business day awareness for penalty deadlines
- Tax module -- Brazilian IOF, grossup, pluggable tax strategy
- Timezone-aware -- UTC by default, configurable globally
- Marshmallow extension -- custom fields for serialization
- SQLAlchemy extension -- column types + loan/settlement bridge with SQL-queryable balance
Installation
pip install money-warp
With optional extensions:
pip install money-warp[marshmallow] # Marshmallow fields
pip install money-warp[sa] # SQLAlchemy types + bridge
Quick Start
from datetime import datetime, timezone
from money_warp import Money, InterestRate, Loan, generate_monthly_dates
from money_warp.tz import to_date
principal = Money("10000.00")
rate = InterestRate("5% a") # 5% annually
start_date = datetime(2024, 1, 15, tzinfo=timezone.utc)
due_dates = [to_date(d) for d in generate_monthly_dates(start_date, 12)]
loan = Loan(principal, rate, due_dates)
schedule = loan.get_amortization_schedule()
print(f"Monthly payment: {schedule[0].payment_amount}")
print(f"Total interest: {schedule.total_interest}")
loan.record_payment(Money("856.07"), datetime(2024, 2, 1, tzinfo=timezone.utc))
print(f"Remaining balance: {loan.current_balance}")
Time Machine
Travel to any date and see the loan exactly as it was -- payments, interest, fines, everything filtered to that moment:
from money_warp import Warp, Loan, Money, InterestRate
from datetime import date, datetime
loan = Loan(Money("10000"), InterestRate("5% a"), [date(2024, 1, 15)])
loan.record_payment(Money("500"), datetime(2024, 1, 10))
loan.record_payment(Money("600"), datetime(2024, 2, 10))
loan.record_payment(Money("700"), datetime(2024, 3, 10))
# Warp to the past -- only payments made by that date are visible
with Warp(loan, datetime(2024, 1, 20)) as past_loan:
print(f"Balance on Jan 20: {past_loan.current_balance}")
# Warp to the future
with Warp(loan, datetime(2025, 1, 1)) as future_loan:
print(f"Balance in 2025: {future_loan.current_balance}")
# Original loan is unchanged
print(f"Present balance: {loan.current_balance}")
Documentation
Full guides, examples, and API reference at tomascorrea.github.io/money-warp.
- Quick Start
- Money and Precision
- Interest Rates
- Percentages
- Cash Flow Analysis
- Date Generation
- Time Machine
- Present Value and IRR
- Fines and Mora Interest
- Tax and IOF
- Timezone Handling
- Marshmallow Extension
- SQLAlchemy Extension
- API Reference
Contributing
Contributions are welcome! See the Contributing Guide for details.
License
MIT -- see LICENSE.
1 maintainer
Metadata
1 maintainer
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