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A Python wrapper for the RtMidi C++ library written with Cython.

Project description


RtMidi is a set of C++ classes which provides a concise and simple, cross-platform API (Application Programming Interface) for realtime MIDI input/output across Linux (ALSA & JACK), Macintosh OS X (CoreMidi & JACK), and Windows (Multimedia Library & Kernel Streaming) operating systems.

python-rtmidi is a Python binding for RtMidi implemented with Cython and provides a thin wrapper around the RtMidi C++ interface. The API is basically the same as the C++ one but with the naming scheme of classes, methods and parameters adapted to the Python PEP-8 conventions and requirements of the Python package naming structure. python-rtmidi supports Python 2 (tested with Python 2.7) and Python 3 (3.2).


python-rtmidi is currently in alpha-stage, which means is is published in the hope that other developers try it out and help finding bugs, and that its API is not yet finalised. What is there should work but is currently only tested thoroughly under Linux ALSA/JACK and less regularly under OS X (CoreMIDI/JACK) and Windows (WinMM). Support for Windows Kernel Streaming API does not work yet due to compilation problems.

Usage example

Here’s a quick example of how to use python-rtmidi to open the first available MIDI output port and send a middle C note on MIDI channel 10:

import time
import rtmidi

midiout = rtmidi.MidiOut()
available_ports = midiout.get_ports()

if available_ports:
    midiout.open_virtual_port("My virtual output")

note_on = [0x99, 60, 112] # channel 10, middle C, velocity 112
note_off = [0x89, 60, 0]

del midiout

More usage examples can be found in the tests directory of the source distribution. API documentation is available by looking at the docstrings in the Cython source code or using tools like pydoc or IPython and by reading the RtMidi documentation.


python-rtmidi is a Python C(++)-extension and therefore a C++ compiler and a build environment as well as some system-dependant libraries are needed. See “Requirements” below for details.

Installer (Windows only)

An installer with a pre-compiled version for Windows with Windows MultiMedia API support is available through PyPI fro some Python versions. Download it from python-rtmidi’s PyPI page and start the installer by double-clicking.

From PyPI

If you have all the dependencies, you should be able to install the package with pip or easy_install:

$ pip install python-rtmidi

or, if you prefer setuptools:

$ easy_install python-rtmidi

This will download the source distribution, compile the extension and install it in your active Python installation. Unless you want to change the Cython source file _rtmidi.pyx, there is no need to have Cython installed.

python-rtmidi also works well with virtualenv and virtualenvwrapper. If you have both installed, creating an isolated environment for testing and using python-rtmidi is as easy as:

$ mkvirtualenv rtmidi
(rtmidi)$ pip install python-rtmidi

From the Source Distribution

Of course, you can also download the source distribution package as a Zip archive or tarball, extract it and install using the common distutils commands, e.g.:

$ wget
$ tar xzf python-rtmidi-0.2a.tar.gz
$ cd python-rtmidi-0.2a
$ python install

From Subversion

Lastly, you can check out the python-rtmidi source code from the Subversion repository and then install it from your working copy. Since the repository does not include the C++ module source code pre-compiled from the Cython source, you’ll also need to install Cython from its Git repository. Using virtualenv/virtualenvwrapper is strongly recommended in this scenario:

$ mkvirtualenv rtmidi
(rtmidi)$ cdvirtualenv
(rtmidi)$ git clone
(rtmidi)$ svn co svn:// python-rtmidi
(rtmidi)$ cd cython
(rtmidi)$ python install
(rtmidi)$ cd ../python-rtmidi
(rtmidi)$ python install


Naturally, you’ll need a C++ compiler and a build environment. See the platform-specific hints below.

Only if you want to change the Cython source file _rtmidi.pyx or want to recompile _rtmidi.cpp with a newer Cython version, you’ll need to install Cython >= 0.17. Currently this version is only available via the Git respository (see Cython web site) as version 0.17pre. The _rtmidi.cpp file in the source distribution was compiled with Cython 0.17pre as of 2012-07-22 and Python 2.7.2.

RtMidi (and therefore python-rtmidi) supports several low-level MIDI libraries on different operating systems. Only one of the available options needs to be present on the target system, but support for more than one can be compiled in. The setup script will try to detect available libraries and should use the appropriate compilations flags automatically.

  • Linux: ALSA, JACK
  • OS X: CoreMIDI, JACK
  • Windows: MultiMedia (MM), Windows Kernel Streaming


For the C++ compiler and the pthread library install the build-essential package on debian-based systems.

Then you’ll need Python development headers and libraries. On Linux, install the python-dev package. If you use the official installers from you should already have these.

To get ALSA support, you must install development files for the libasound library (debian package: libasound-dev). For JACK support, install the libjack development files (libjack-dev or libjack-jackd2-dev).


Install the latest Xcode or g++ from MacPorts or homebrew (untested). CoreMIDI support comes with installing Xcode. For JACK support, install JACK for OS X with the full installer.


On Windows you’ll need Visual Studio 2008 Express. Visual Studio 2010 (Express) or later editions will not work with current official Python distributons. After you have installed the Visual Studio, you probably need to edit the WINLIB_DIR and WININC_DIR variables at the top of the file to point to the location of WinMM.lib and the Microsoft SDK headers.

Compiling python-rtmidi with Windows Kernel Streaming support currently does not work due to syntax errors in RtMidi.cpp. This is currentyl being investigated. You can exclude Windows Kernel Streaming Support by providing the --no-winks option to the invocation.

Compiling with MinGW also does not work out-of-the-box yet. If you have any useful hints, please let the author know.

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