[GNC] Working with compound interest on varying amounts

Tue Dec 4 19:10:09 EST 2018

GnuCash requires Python3 for the python bindings, and in order for them to work in the bundle I’d have to add python3 to it. It’s too big to burden the 99% of users who aren’t interested in Python bindings so it’s not in the bundle.

If you’re comfortable building software you can also build your own stand-alone GnuCash with the Python bindings enabled, see https://wiki.gnucash.org/wiki/MacOS/Quartz.

Regards,
John Ralls

> On Dec 5, 2018, at 8:58 AM, Hal Vaughan <hal at hal.dance> wrote:
> 
> 
> This gave me enough to tell me it’s worth it to take time to look into this.  (I’ve found so many times I can spend hours or more just looking into questions on some programs only to find out I can’t do anything close to what I want or need to do.)  Often I find it helps to just ask a community, "Can I do this with this program?"  It can be tough to dive into a new API or system just to find out if a task is even doable.  (Or if it can be done without months of work!)
> 
> I found GnuCash does have an API with Python bindings, but on the iMac, I would have to access it through MacPorts.  I’ve used MacPorts before and like a lot of what it offers, but I’ve also had it really mess a few things up.  (For instance the MacPorts Perl, Python and other scripting languages pre-empt the native versions on macOS.  I’ve had that create serious problems with system and library updates in the past.)  I refuse to use MacPorts because it’s caused me significant problems in the past.
> 
> But even knowing that the ledger is in XML and that the entries can be edited outside of the program tells me all I need to know. I’ll be following up on the appropriate GnuCash mailing list.
> 
> Thanks for that info!
> 
> 
>> On Dec 4, 2018, at 4:47 PM, 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 did find a little on the API.  I’d be working in Python, since my simple ledger libraries are in Python.  But Python bindings, on an iMac, are in MacPorts.  My comments at the top address MacPorts.
> 
>>> 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.
> 
> That’s a big help.  XML can easily be worked with, so it’s not hard to study or find the format info so I can add entries if I need to.
> 
> Thanks for the info!
> 
> 
> Hal
> 
> 
>> (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
>> kg7je at arrl.net
>> 253-350-0166
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