On Saturday, March 14, 2026 at 12:19:28 AM UTC+10:30 Chary Ev2geny wrote:

On Friday, March 13, 2026 at 12:46:02 PM UTC+1 [email protected] wrote:

so I'm off to convert my collection of scripts & Google Sheet/beancount 
hybrids & jupyter notebooks to Marimo......


Just out of curiosity, How did you use  Google Sheets in all of this?


Google Sheets provides a "good enough" UI/front-end with charts, stock 
prices & exchange rates (which update orders of magnitude faster than 
bean-price), and a convenient place to keep data that doesn't fit nicely 
into beancount itself (such as joint life expectancy). It is also easy to 
store historical information (like daily net worth or historical dividend 
rates) rather than try to pull it from beancount each time I need it 
(impractical for net worth, somewhat annoying for other things). It is 
easily accessible via mobile and is cloud hosted so I can see it anywhere. 
I've had the Google Sheet for over a decade and it has accumulated a lot of 
things I don't actually use anymore.

My primary use for it is to take our current net worth and run a PMT 
calculation on it using joint life expectancy and expected returns to 
calculate how much we can safely spend each year. It is nice that this 
happens "automatically" and I don't need to run some script to see it, I 
just open up the sheet on any device and there it is. (There is no native 
PMT in python but the numpy_financial package provides it.)

I've also used PMT when looking at various debt paydown scenarios and how 
much free cash flow remains after. I can't get a normal home mortgage so 
have used portfolio margin to buy property in the past but there is no 
convenient vendor-calculated "monthly mortgage payment" with that, so you 
sort of need to manage it yourself to make sure you stay on top of the 
accruing interest.

It shows us how much charitable giving we should target -- based on an 
heuristic from Peter Singer's book/website The Life You Can Save.

Because net worth is stored daily it is easy to look up, or chart, 
historical data. For instance, after a major purchase (property, car) how 
long does it take our portfolio to recover (currently 553 days and 
counting, the Iran was isn't helping....)

There's a table showing various projected safe spending rates (based on PMT 
above) at various net worths that let us have reasonable conversations 
about increasing/decreasing spending in the coming years (where "spending" 
including gifting both family and charities).

In the far distant past I used it for investigating things like Siegel & 
Waring's "Only Spending Rule You'll Ever Need", Walton target portfolio 
sizes, Stout & Mitchell's spending rule, Blanchett's Simple Formula, 
Steiner's Corridor, Kasten's Model, Milevsky's Stochastic Portfolio Value, 
and so on.

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