[GNC] Working with compound interest on varying amounts

[John Ralls]

The API documentation is at https://code.gnucash.org/docs/MAINT <https://code.gnucash.org/docs/MAINT>. It’s for the C/C++ API but the python bindings follow that pretty closely; there’s some python-specific documentation at https://code.gnucash.org/docs/MAINT/python_bindings_page.html <https://code.gnucash.org/docs/MAINT/python_bindings_page.html> and some more information at https://wiki.gnucash.org/wiki/Python_Bindings <https://wiki.gnucash.org/wiki/Python_Bindings>.

Sébastien will come along and suggest piecash (https://github.com/sdementen/piecash <https://github.com/sdementen/piecash>) so I’ll save him the trouble ;-). Note that piecash doesn’t implement any of GnuCash’s business logic so it’s up to the user to ensure that everything is in balance. Note as well that piecash works only with SQLite3, not XML.

Regards,
John Ralls


> On Dec 5, 2018, at 6:47 AM, Stephen M. Butler <kg7je at arrl.net> wrote:
> 
> On 12/4/18 6:56 AM, Hal Vaughan wrote:
>> Let me add another thought to this.  I’m putting it on the original thread, since it really would be something I’m tempted to ask in response to several answers.
>> 
>> I already have routines, in Python, that do this in my own ledger program.  However, I’m really trying to move away from doing any development work on software I use for professional work.  (In other words, for my own sanity, I’m trying to draw a line and keep programming for hobby stuff now and not do any programming for my real estate and investment work.)
> 
> 
> While I have not used them (yet), I understand that there is an API available to handle most transactions and all back-end interaction to the data store.
> 
> I haven't found the API documentation yet.
> 
>> I think I’ve read that the GnuCash ledger is in XML or an open format.  How hard would it be to add transactions to the ledger? And is it possible to call, say, a Python script from any extension menu in the program?  I’m on an iMac and can always run the Python script on my own if needed.
> 
> 
> XML is the default storage (compressed).  Options include some database environments.
> 
>> (I’m wondering if I researched this before.  I’m asking now just to know if it’s possible - if it is, I’ll be glad to dig in and find what I need, but I’d rather know if it’s worth exploring before trying to jump in.)
>> 
>> 
>> Thank you!
>> 
>> Hal
>> 
>>> On Dec 3, 2018, at 1:38 AM, Hal Vaughan <hal at hal.dance> wrote:
>>> 
>>> For the past few years, for my business that is mostly about renovating or restoring houses and reselling them (not flipping - this work takes time), I’ve used a Python library I wrote myself to handle accounting.  It was basically made up mostly of stuff I had, with a few new things added in.
>>> 
>>> I would like to switch over to GnuCash.  Luckily, since I’m at a slow point and between projects, I can do that without worrying about converting old data for older LLCs and projects.
>>> 
>>> There’s one issue I’m not sure can be handled by GnuCash, so I’d like to find out about it before trying to switch over.
>>> 
>>> I use a line of credit.  Luckily the interest rate is basically constant.  (There’s a slight flux, but not much.)  The problem is its compounded and, of course, every time I withdraw money from the credit line or pay any back, the principal amount changes. I’m hoping, at this point, people are saying, "Oh, yeah, just do this…."
>>> 
>>> But just in case there’s a need for clarification, if I withdraw $50,000 to purchase a house on January 1, then, on the 15th, withdraw $10,000 for roofing work, need to figure out the total owed to that credit line on 1/31, and the interest rate is 3%, then I have to figure compound interest on $50,000 at 3% from 1/1 to 1/15.  Then I have to add $10,000 to that amount to calculate the interest on the $50,000 plus 15 days of interest, plus $10,000, plus the interest from the 15th to the 30th, at 3%, to get a clear number for what I owe.
>>> 
>>> Can I have this done automatically on an account?  If not, how can I easily keep track of this in GnuCash?
>>> 
>>> 
>>> Thank you!
>>> 
>>> 
>>> Hal
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> 
> -- 
> Stephen M Butler, PMP, PSM
> Stephen.M.Butler51 at gmail.com <mailto:Stephen.M.Butler51 at gmail.com>
> kg7je at arrl.net <mailto:kg7je at arrl.net>
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