View source for Python Bindings

[[Category:Python]]
Python in gnucash has two main aspects:

* Python bindings
* [[Python shell]]

;Python bindings: provide SWIG wrapper functions for some of GnuCash' C/C++ [[Using the API|API]]. They can be used to write standalone scripts to work with the GnuCash financial data. In the source tree they are located at bindings/python. 

;The python shell: on the other hand (if enabled) opens at GnuCash startup and provides a python environment to use with the running GnuCash instance. In the source tree it is located at gnucash/python. The python bindings can be used in this shell. Be careful: GnuCash is not designed to have multiple instances manipulating the data at the same time, reading should be safe though.

;Other:Note there is also an independent project that offers a pure python client, [https://piecash.readthedocs.io/ piecash], to read and manipulate GnuCash books if saved in of the three SQL backends (sqlite, MySQL, Postgres). This is not endorsed by the GnuCash developers as it's not using the gnucash api to manipulate your data. Use with caution.
:Currently (Oct 2020), piecash supports files created up to GnuCash 4.2.

= General notice =
Python bindings have been added to gnucash in 2008 or earlier.  There is still very little documentation and probably few people would know how to use it.  While not a manual, this page was created in the hope to provide information for those interested in gnucash and python. Python bindings are not installed on Windows.

See also
* <s>http://article.gmane.org/gmane.comp.gnome.apps.gnucash.devel/23800</s><ref name='broken_link'>Links to gmane are broken since several years. To avoid it, please link to [[Mailing Lists#Existing Lists|our mailing list archives]]!</ref> "Re: documentation for python bindings" and
* <s>http://article.gmane.org/gmane.comp.gnome.apps.gnucash.devel/23613</s><ref name='broken_link'/> "Re: documentation for python bindings" with some pointers on how to look up the existing documentation
* Perhaps it was this thread: [{{URL:mail archive|devel}}2008-July/023431.html documentation for python bindings]

= Setting things up =

== Python package ==

A Python package must be installed:
;Gnucash {{MainVersion}}.x: requires Python ≥ {{Python_Version}}.
;GnuCash 3.x: GnuCash's Python bindings has been known to work with [{{URL:wp}}CPython CPython] version 3.2 or later as of GnuCash 3.0.

== GnuCash ==

On the other hand one needs a GnuCash package with python bindings enabled. Most linux distributions either build GnuCash with these bindings enabled by default or provide it via a separate package, usually named <tt>python{{Python Major}}-gnucash</TT> or something similar. For example:
;Enabled by default: The GnuCash packages in '''Archlinux''' and '''Fedora''' have been built with the python bindings enabled by default.
;Split in a separate package: In '''Debian''' based distributions like '''Ubuntu''' the easiest way to install the GnuCash Python bindings is via apt-get: <syntaxhighlight lang="sh">
sudo apt-get install python3-gnucash
</syntaxhighlight>

;Building from source: It is also possible to use python bindings when building gnucash from source yourself. In this case you need to make sure the bindings are enabled while configuring the build, for example with<syntaxhighlight lang="sh">
cmake -DWITH_PYTHON=ON $OTHER_OPTIONS
</syntaxhighlight>

;Notes:
:- If you are bulding GnuCash yourself see [[CMake#GnuCash Configuration Variables]] for the OTHER_OPTIONS.
:- The flatpaks we create currently don't ship with python bindings enabled
:- Similarly we don't ship python bindings with our Windows and MacOS packages. It may be possible to build Windows and MacOS packages yourself based on our Windows and MacOS build scripts (by enabling python bindings during the build), but I have not tested this.

== Prepare the environment ==

If you are using a distribution package, you are probably all set and can skip this step. Similarly if you build gnucash and install it in the default system location (/usr/local), what follows is probably not necessary.

However if you are building from source (on any platform) but install into a non-default location, or don't install at all you will need to set up a few environment variables to help gnucash and python to find each other and their dependencies (like where gnucash can find its gsettings schema). Consult [[Directory Standards#XDG]] for defaults.

=== Build and install ===

These apply when you have built and installed gnucash from source.

In what follows you should set '''INST_DIR''' to the path where gnucash is installed during your build. This is often referred to as the installation prefix or something similar.

<syntaxhighlight lang="sh">
INST_DIR=xyz           # Point this to the actual directory gnucash was installed in !!
PYTHONPATH=$INST_DIR/lib64/python3.6/site-packages:$PYTHONPATH
XDG_DATA_DIRS=$INST_DIR/share:${XDG_DATA_DIRS}
export PYTHONPATH XDG_DATA_DIRS
# More path settings may be needed to interface with the guile bindings (if that's possible) or finance::quote
# You can check prefix/etc/gnucash/environment for the full list the gnucash sets up for itself
</syntaxhighlight>
;Note: <q>3.6</q> should match the python version used to build GnuCash.

[[User:Kohtala]] notes that if even if you install to the default CMAKE_INSTALL_PREFIX of /usr/local, the Ubuntu/Debian python is compiled to search for packages in dist-packages and does not find them in site-packages. So you may have to change the PYTHONPATH line above accordingly.

=== Build ===

It is also possible to use the python bindings from the gnucash build directory. During development that saves an extra install step for each code iteration. However this needs you to set up two more parameters in addition to those set up when gnucash is installed and we need to point at the build directory instead of the install directory.

In what follows you should set '''BUILD_DIR''' to the path where gnucash is built. This is the directory in which cmake and make/ninja are executed.

<syntaxhighlight lang="sh">
BUILD_DIR=xyz           # Point this to the actual directory gnucash was installed in !!
PYTHONPATH=$BUILD_DIR/lib64/python3.6/site-packages:$PYTHONPATH
XDG_DATA_DIRS=$BUILD_DIR/share:${XDG_DATA_DIRS}
GNC_UNINSTALLED=1
GNC_BUILDDIR=$BUILD_DIR
export PYTHONPATH XDG_DATA_DIRS GNC_UNINSTALLED GNC_BUILDDIR
# More path settings may be needed to interface with the guile bindings (if that's possible) or finance::quote
# You can check prefix/etc/gnucash/environment for the full list the gnucash sets up for itself
</syntaxhighlight>
;Note: <q>3.6</q> should match the python version used to build GnuCash.

==Interactive Shell==
I use [{{URL:wp}}IPython IPython] for an interactive shell.  If you prefer something else, let us know if there is any difference.

If you have followed the setup steps above you can either start up an interactive python session with ipython <syntaxhighlight lang="sh">
ipython
</syntaxhighlight> or call your script to be executed <syntaxhighlight lang="sh">
python /path/to/script
</syntaxhighlight>
;Notes
:To install ipython run <syntaxhighlight lang="sh">
sudo pip ipython
</syntaxhighlight>
:[https://pypi.org/project/pip/ pip] is the package installer for Python.

== Mac OSX ==

# Install GnuCash via [https://www.macports.org/ MacPorts]: <syntaxhighlight lang="sh">
sudo port install gnucash +python36
</syntaxhighlight>
#;Notes:
#:# <q>36</q> should now be <q>{{Python_Version_short}}</q>.
#:# at the time of writing, only the non-quartz environment is supported.
# Setup the PYTHONPATH to point to your macports install: <syntaxhighlight lang="sh">
export PYTHONPATH=$PYTHONPATH:/opt/local/lib/python3.6/site-packages 
</syntaxhighlight>
#;Note: <q>3.6</q> should now be <q>{{Python_Version}}</q>.

You can then either start up an interactive python session with ipython or call your script to be executed: <syntaxhighlight lang="sh">
ipython
python /path/to/script
</syntaxhighlight>

= Documentation =

As pointed out in the introductory paragraph, the documentation is rather slim at this point in time. Below you will find some sources where you might be able to find what you are looking for. Generally speaking, this is not yet end-user friendly stuff.

== Principles ==

Python bindings provide SWIG wrapper functions for some of gnucashs C/C++ [[Using the API|API]]. They can be used to write standalone scripts to work with the gnucash financial data.

=== What SWIG does ===
* see [{{URL:docs:API}}python_bindings_page.html API: python-bindings (stable branch)]

=== How to use the Python bindings ===
* see [{{URL:docs:API}}python_bindings_page.html API: python-bindings (stable branch)]

= Further Docs =

== Doxygen ==
Have a look at the [{{URL:docs:API}}python_bindings_page.html python-bindings (stable branch)] or, if it exists [{{URL:docs:API|FUTURE}}python_bindings_page.html python-bindings (future branch)] in the [[Doxygen|doxygen]] '''API documentation'''.
* [{{URL:docs:API}}group__Business.html business functions documentation]
* [{{URL:docs:API}}group__python__bindings__examples.html Example scripts]

== Github ==
The source code of gnucash including the python bindings can be accessed on [{{GitURL}} github].

* [{{URL:git}}gnucash/tree/stable/bindings/python/example_scripts Example scripts] from the source code.

== Inside python ==

Using python or ipython there is some sparse help:

big long list of stuff <syntaxhighlight lang="py">
import gnucash.gnucash_core_c
help(gnucash.gnucash_core_c)
dir(gnucash.gnucash_core_c)
</syntaxhighlight>

higher abstraction level help <syntaxhighlight lang="py">
import gnucash.gnucash_core
import gnucash.gnucash_business
help(gnucash.gnucash_core)
help(gnucash.gnucash_business)
</syntaxhighlight>

== Mailing list ==

Again, <s>http://article.gmane.org/gmane.comp.gnome.apps.gnucash.devel/23613</s><ref name='broken_link'/> contained some more hopefully useful pointers, but the page is no longer available.

= Example Usages =
This section should contain some pointers to scripts using the GnuCash Python bindings:

* {{URL:GH}}hjacobs/gnucash-qif-import --- imports transactions from QIF text files into GnuCash's own file format
* {{URL:GH}}hjacobs/gnucash-stock-portfolio --- script using the GnuCash commodity/price table
* {{URL:GH}}hjacobs/gnucash-fiximports --- tries to fix target accounts using regular expression rules (e.g. PIZZA -> Expenses:Dining)
* [{{URL:GL}}wiese28/gnucash-happy-new-year/ Happy New Year] --- A full Python program to generate a new GnuCash file at the beginning of a new accounting period.

;Important: GnuCash uses '''DeprecationWarnings,''' which are disabled by default in Python. Be sure to test periodically with <tt>python -Wd</tt> or with <tt>PYTHONWARNINGS=default</tt> set in the environment so that you know about API that will disappear in the next major release. See [[Development_Process#LibGnuCash API Stability]] for the policy.