oct2py 1.0.0

Python to GNU Octave bridge --> run m-files from python.

oct2py - Python to GNU Octave bridge.

Overview

Uses Octave to run commands and m-files. Run:

>>> import oct2py
>>> oct2py.demo()

for a live demo of features. Supports any Octave function or m-file, passing the data seamlessly between Python and Octave using MAT files. If you want to run legacy m-files, do not have MATLAB®, and do not fully trust a code translator, this is your library.

IPython Notebook Integration

Oct2py is used by IPython to enable %octavemagic, to include inline plotting. See example here.

New in Version 1.0.0

• Support for Python3.3

• Support for logging (e.g. oc = Oct2Py(logger=my_logger))

• Oct2Py can be used as a context manger (with Oct2Py() as oc:)

• Support for unicode characters

• Improved support for cell array and sparse matrices

• Bug fix: Changes to user m. files were not updated during a session

• Bug fix: Removed popup console window on Windows

• Thanks to @stefanv, @jenshnielsen, @idella, @klonuo, @Juanlu001, @bj0, @graingert, @jordigh, @wannesm, and Konstantin Markov for helping to get this out of beta.

Installation

You must have GNU Octave installed and in your PATH. On Windows, the easiest way to get Octave is to use an installer from sourceforge. On Linux, it should be available from your package manager. Additionally, you must have the numpy and scipy libraries installed, then run:

python setup.py install

or:

pip install oct2py

or:

easy_install oct2py

Note for Windows users: You may have to follow these instructions in order to use inline figures in IPython (or specify -f svg).

Datatypes

All Octave variable types are mapped to comparable Python types. See Oct2Py Data Conversions in the documentation for a full list. Wherever possible, value and type are preserved on a roundtrip to Octave. For example, if you send an ndarray of type np.int8, Octave receives an int8 matrix, and the value returned would be the original array, of type np.int8. Almost all Python types can be sent to Octave (including ndarrays of arbitrary rank) and read back in the same form. Note that dictionaries are mapped to Octave structures, which are returned as Struct objects. These objects behave just like an Octave struct, but can be accessed as a dictionary as well:

>>> from oct2py import Struct
>>> a = Struct()
>>> a.b = 'spam'  # a["b"] == 'spam'
>>> a.c.d = 'eggs'  # a.c["d"] == 'eggs'
>>> print a
{'c': {'d': 'eggs'}, 'b': 'spam'}

Performance

There is a penalty for passing data via MAT files. Running speed_test.py shows the effect. After a startup time for the Octave engine (<1s typically), raw function calls take almost no penalty. The penalty for reading and writing from the MAT file is around 1-2ms on my laptop. This penalty is felt for both incoming and outgoing values. As the data becomes larger, the delay begins to increase (somewhere around a 100x100 array). If you have any loops, you would be better served using a raw “run” command for the loop rather than implementing the loop in python:

>>> import oct2py
>>> oct2py.speed_test()

Plotting

Plotting commands do not automatically result in the window being displayed by python. In order to force the plot to be drawn, the command “figure(gcf() + 1);’” is tacked onto anything that looks like a plot command, when called using this package. If you have plot statements in your function that you would like to display, you must add that line after each plot statement.

Thread Safety

Each instance of the Octave object has an independent session of Octave and uses independent random MAT files. The library therefore should be thread safe. See thread_test.py for an example of several objects writing a different value for the same variable name simultaneously and successfully retrieving their own result:

>>> import oct2py
>>> oct2py.thread_test()

Note for MATLAB® users

Octave supports most but not all of the core syntax and commands. The main noticable differences are nested functions are not allowed, and GUIs (including uigetfile, etc.) are not supported. There are several Octave packages (think toolboxes), including image and statistics.

Similar work

• pytave - Python to Octave bridge, but does not run on win32 (which is the reason for this library).

• mlabwrap - Python to MATLAB® bridge, requires a MATLAB® license. The oct2py library API is modeled after mlabwrap.

• ompc, smop - Matlab to Python conversion tools. Both rely on effective parsing of code and a runtime helper library. Ideally one or both of these projects render this one unnecessary. The idea of using introspection to find “nargout” was borrowed from the ompc project.

CI Status

oct2py has automatic testing enabled through the convenient Travis CI project. Here is the latest build status: