Molflow

Python interface to MATLAB (pymatlab)

This package lets Python users interface and communicate with MATLAB from Python. Pymatlab makes it easier for users to integrate a project with a large MATLAB codebase into python scripts by using MATLAB scripts as a part of the python program.

The basic functionality of this package is to send data from Python to MATLAB's workspace to be able to run Matlab function on the data. After processing you retrieve back data to python. This enables you to process data with Mathlab's built in functions, toolboxes or Matlab-scripts. It is also possible to use MATLAB's to generate plots or other graphics.

The package uses Numpy's ndarrays and translates them into MATLAB's mxarrays using Python's ctypes and Matlab's mx library. The interface to MATLAB's workspace in done through MATLAB's engine library.

Download

Downloading is possible from PyPi and SourceForge pymatlab files. Since pymatlab is hosted at SourceForge the latest development version is available from git. There are different branches available this is the ctypes variant.

Installing

Standard installation method using pip, easy_install or 'python setup.py install'.

Preparing to use pymatlab

You need MATLAB from Mathworks properly installed on your local machine.

Linux:

C-shell has to be installed in order to make the Matlab connection work. Also the path to the matlab binary needs to be set.

$ sudo apt-get install csh $ export PATH = /opt/MATLAB/R2013a/bin:$PATH

Win:

On Windows make sure the Matlab DLLs are in your "Path" environment variable. This version is not tested in Windows but should be possible to run with some debugging efforts.

Requirements

Limitations

The current version lets you transfer arrays of any rank between Python and Matlab using the following datatypes: Single and double precision floatpoint numbers. Integer numbers of different bit lengths (8-64) unsigned or signed. Complex numbers (single or double precision). Logical arrays. Any other types will probably fail or give unpredictable results.

Using pymatlab

First import:

>>> import pymatlab

Initialise the interpretor.

>>> session = pymatlab.session_factory()

Create an numpy-array to start the work.

>>> from numpy.random import randn
>>> a = randn(20,10,30)

Send the numpy array a to the MATLAB Workspace to the variable 'A'

>>> session.putvalue('A',a)

Do something in matlab in MATLAB with variable A. Sucessfull commands return an empty string - if MATLAB generates an error the returning string holds the error message

>>> session.run('B=2*A')
>>> session.run('C')
Traceback (most recent call last):
    ...
RuntimeError: Error from Matlab: Error: MATLAB:UndefinedFunction with message: Undefined function or variable 'C'.
<BLANKLINE>

A trick to make larger scripts more failsafe with regards to syntax errors. Send a script to a string variable and run it with eval().

>>> mscript = """D = A
... for i=1:10
...    D = 2*D
... end
... """
>>> session.putvalue('MSCRIPT',mscript)
>>> session.run('eval(MSCRIPT)')

To retrive the variable back to python:

>>> b = session.getvalue('B')
>>> (2*a==b).all()
True

If you want to explicitly close the connection to the interpreter delete the instance. Normally Matlab will be close when the session variable runs out of scope.

>>> del session

Bugs, support and feature requests

All bug reports, feature requests or support questions are directed to to pymatlab@molflow.com.

Please consider to support us in our efforts by donating to pymatlab. Your donations will be used to buy hardware and software licenses to be able to continue to develop this package.