Python bindings: patch, documentation, examples

[David Osguthorpe]

On Thu, May 08, 2014 at 11:47:34PM -0700, mshapiro wrote:
> David Osguthorpe wrote
> > I have a very hacky implementation in gnucash to call python from guile
> > and
> > return results to guile - I found existing libraries to do both
> > (no updates to gnucash required - just a user prototype.scm file)
> 
> Can you post what libraries you used, where you got them, how to use them
> and your prototype.scm file.  Also, any pointers to useful documentation for
> using the Python bindings would be greatly appreciated.  I am primarily
> interested (at the moment) in accessing budgeting information and future
> transactions, as well as accounts, since I would like to do more forecasting
> than the standard reports provide.
> 

it is really hacky - and I still had crashes when attempting to create real reports
so its very, very alpha
but if you wish to pursue it here are the details

note this does not use any of the python bindings - as far as I can tell they only work for
non-gui standalone scripts - well its the only Ive used them
- you would write a script to access your gnucash database (xml or SQL) and use any python
modules to format the data for a new report completely outside of gnucash
for the moment I would say you would be better just writing command line scripts
using the python bindings to generate HTML or whatever reports

here are some details

1. you need pyguile - a module for calling guile version of scheme from python
- unfortunately the available source has not been udpated for years so needed quite
a bit of patching to build (I run under macports on OSX mainly)
- one patch I did have to add was the ability to return so called SCM (scheme) objects
back to guile

2. you need schemepy - which has a module for calling python from guile version of scheme
- again the available source has not been udpated for years so needed
some patching to get running

Then you have the prototype.scm (simply not bothered to change name) which sets up
to call python where you could write your report. 


My initial goal was to write reports in python - Im primarily writing in this now
and although I had tried scheme for a multiple stock price scatter plot report every time I went
back trying to re-think in scheme was a pain

The major problem I ran across is that when analysing the GUI report system in gnucash
I discovered it was not done in pure gtk but some of the gui is actually written in scheme
by calling gtk gunctions via swig wrapped functions involving gtk
- to directly call python reports would need re-writing most of this GUI scheme stuff using
the python gtk library - not difficult but seemed like a lot of work
I had hoped to find a report function where I could plugin in a call to python so could then
do the report in python (python has the ctypes module which allows calling C functions
in  arbitrary C shared libraries such as gnucash uses) - pygtk allows direct use of gtk functions
in python
I did this around 2.4.7 and am looking to review it now at 2.6.3

from that analysis as far as I could tell the final report result is an html text string which is
written to a file - again these components using scheme coding


If you really want the files let me know

as you have discovered there isnt much documentation of the python bindings
I have some scripts and gnucash binding extensions - Ive been updating them because
of the changes between 2.4 and 2.6 - I tend to use lots of comments to document
what I discover as I use the bindings - youre welcome to them as well
(I also have some updates to the swig bindings which my extensions/script use which
I have not posted as patches because still figuring the changes from 2.4 to 2.6)

David