Financials

financials/ABOUT.md

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+### Interest
+
+* Compound Interest: "Compound interest is calculated by multiplying the initial principal amount by one plus the annual interest rate raised to the number of compound periods minus one." [Compound Interest](https://www.investopedia.com/) 
+* Simple Interest: "Simple interest paid or received over a certain period is a fixed percentage of the principal amount that was borrowed or lent. " [Simple Interest](https://www.investopedia.com/)
+* 

financials/interest.py

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+from __future__ import annotations
+
+def simple_interest(principle:float, daily_interest_rate:float, number_of_days_between_payment:int) -> float:
+    """
+    >>> simple_interest(18000,0.06,3)
+    3240.0
+    """
+    result = principle * daily_interest_rate * number_of_days_between_payment
+    return result
+
+def compound_interest(principle:float, nominal_annual_interest_rate_percentage:float, number_of_compounding_periods:int)-> float:
+    """
+    >>> compound_interest(10000,0.05,3)
+    1576.2500000000014
+    """
+    result = principle * ((1 + nominal_annual_interest_rate_percentage) ** number_of_compounding_periods - 1)
+    return result
+
+
+if __name__ == "__main__":
+    import doctest
+
+    doctest.testmod()