Simple Amortizing Bond Model App

I built a simple amortizing bond model application using python and Streamlit. This is a follow-up to my series of posts on amortizing bond models. The app lets the user quickly examine a bunch of simple models by varying the parameters.

This is version one of the app. It implements a simple bond model with a simple growing/shrinking revenue curve which the user controls. It’s set up to be one term bond, priced to maturity. It can handle premium and discount pricing. It also generates a simple sources and uses table, including percentage-based cost of issuance and a toggle for a market-standard debt service reserve fund.

For version two, I’m planning to implement the following changes:

• Arbitrary revenue curve input;
• Automatically calculated capitalized interest with a toggle for whether or not to respect the IRS 3-year limit;
• Arbitrary ongoing fees, on top of debt service;
• A debt service coverage ratio calculation; and
• Date-based inputs for dated date, maturity date, and principal payments.

For version three, I’m planning to add even more features:

• Arbitrary pricing scale inputs, including serial/term bond structures;
• TIC and arb yield calculations;
• Annual/semiannual amortization options; and
• Warning messages pointing out common structuring issues.