[Edu-sig] re: financial calculation

[Guido van Rossum]

> ____________________________________________________________
> from __future__ import division
> 
> import datetime
> import math
> 
> def future_value(iday,cday,ivalue,cvalue,years):
>    days_invested=(cday-iday).days
>    year_periods=365/days_invested
>    annualized_rate = math.log(cvalue/ivalue)*year_periods
>    #future_value at the end of given years
>    return ivalue*math.pow(math.e,annualized_rate*years)
> 
> #date we purchased stock
> iday=datetime.date(2004,12,27)
> 
> #date of valuation
> cday=datetime.date(2005,2,11)
> 
> #price at purchase
> ivalue=64.5
> 
> #current price
> cvalue=81
> 
> #let's keep this up for ten years  - sure....
> print future_value(iday,cday,ivalue,cvalue,10)
> _________________________________________________
> 
> which returns
> 4561078546.84

If you fix it, as follows:

  year_periods=days_invested/365

the answer is about 85. :-)

-- 
--Guido van Rossum (home page: http://www.python.org/~guido/)