Andrea Grandi

Introduction

My name's Andrea Grandi, I'm italian and I'm a Maemo user/lover/contributor since the Nokia 770. I love Python as development language and few months ago I also gave some contributions to the PyMaemo project.

In these days I had the idea to start writing a Twitter client for Maemo with a precise direction in my mind. I'll try to explain all my reasons here. First of all I've to thank the author of Mauku client. I use it since its first version and I'm quite happy with it. Then, why do I want to write another one?

1. Maemo (MeeGo) is moving to Qt and for this reason I'm going to use Qt, while Mauku uses Gtk.
2. I'm learning Qt and what is better than writing a complete (but not too complex) application to learn better?
3. Mauku is not free as lot of people could think. Reading the source codeyou find this "You are NOT allowed to modify or redistribute the source code.", while I want to write a client and release it under GPL2 or GPL3 license.
4. Mauku is not updated since some months and we have no news about it.
5. I love Python and I like to write free software in this language.
6. I want to give to Maemo a stronger contribute.

My request for help

Before lot of people start writing their own client resulting in 4-5 twitter clients for Maemo, why don't we join our strength and work to a common project? I'm not a Python expert nor a Qt one, but I've some experience as project/team leader and since this is not a complex project, I would be glad to lead it. So, I'm looking for Python developers, Qt developers, UI designers and whoever want to contribute to this project. I still have to find a good name and logo for this application.

Who want to help me?

Quim Gil just confirmed the UX hackfest in Barcelona for 4, 5, 6 december: http://talk.maemo.org/showthread.php?t=33719

What is UX hackfest?
It's a three days meeting for Maemo developers, UX experts and people who want to learn about designing good user interfaces.

When?
On 4, 5, 6 december 2009

Where?
Barcelona, Spain. The exact location has still to be confirmed, but it should be http://citilab.eu

How many people invited?
About 50 people invited (Maemo developers, UX experts, ecc....)

If you are a Maemo developer and you have good user interface designer skills, this is the place for you.

If you are a Maemo developer and you are not a UX expert, this IS anyway the place for you: you'll have the possibility to talk with experts and improve your knowledge about UI design.

Anyone interested, please join the discussion here: http://talk.maemo.org/showthread.php?t=33719

Update 3/11/2009 - 16:00: a wiki page with all information has been created here: http://wiki.maemo.org/Maemo-Barcelona_Long_Weekend
please add your name/data to the page if you requested to join the UX hackfest.

In the last post of this series, we saw how to write a simple binding and we finished to build and install it manually. This is of course not a good way to manage the building/installation procedure.

In Python we can use a library called distutils that let us to automatize the building and installing process. I'll use the foo source code to create the package, so it will be easier to understand.

Using distutils

All we have to do is to write a setup.py file similar to this one:

from distutils.core import setup, Extension

foomodule = Extension('foo', sources = ['foo.c'])

setup (name = 'Foo',
       version = '1.0',
       description = 'This is a package for Foo',
       ext_modules = [foomodule])

As you can see, we have to first import needed modules with: from distutils.core import setup, Extension
then we create an entry for each module we have (in this case just one, "foomodule"). We then call the setup() method passing it all the parameters and our setup.py is complete.

Building and installing

To test it we can try to build the package in this way:

python2.5 setup.py build

if we want to install the module in our system:

python2.5 setup.py install

References

• Official Python documentation: http://docs.python.org/extending/building.html

The PyMaemo team is pleased to announce the second beta release of PyMaemo for Fremantle!

This new release is available through the extras-devel repository, see installation instructions in
http://pymaemo.garage.maemo.org/sdk_installation.html#fremantle

What is it?

Python for Maemo (PyMaemo for short) main objective is to make possible to use Python programming language as the scripting and development language for Maemo Platform, providing a better alternative for fast prototyping and programming in Maemo environment besides the C programming language.

Python is for serious programming and to have fun. Python has a nice syntax, it is easy to learn and powerful enough for a vast range of applications, this is why we choose Python for Maemo.

What has changed?

New packages:

• python-mafw (0.1-1maemo1)
  • Python bindings for the Media Application Framework [1]
  • Supported API is very basic at the moment, and there are some bugs. Feedback is welcome!
• python-hildondesktop (0.0.3-1maemo1)
  • Python bindings for the home/status widgets API
• python-notify (0.1.1-2maemo1)
  • Python bindings for libnotify
• pyclutter (0.8.0-1maemo2)
  • Python bindings for the Clutter API [2]
  • Experimental package, waiting for developer feedback

Updated packages:

• gnome-python (2.26.1-1maemo1)
  • major upgrade, matching current Debian testing release;
  • feedback on this is welcome, as it replaces a fairly old version (2.18).
• pygtk (2.12.1-6maemo7)
  • Enable glade support.
• python2.5 (2.5.4-1maemo1)
  • Updated to latest upstream 2.5.x release.
  • add support to --install-layout=deb flag.
• python-central (0.6.11.1maemo1)
  • dependency needed by the new python-setuptools version.
• python-defaults (2.5.2-3maemo3)
  • Change PREVVER in debian/rules, avoiding old python2.5-minimal versions that had "/usr/bin/python" and thus conflicts with python-minimal.
• python-hildon (0.9.0-1maemo10)
  • lots of bug fixes
• python-setuptools (0.6c9-1maemo1)
  • add support to --install-layout=deb flag.

Bugs fixed: MB#4530 [3], MB#4450 [4], MB#4629 [5], MB#4628 [6],
MB#4647 [7], MB#4632 [8],  MB#4646 [9],  MB#4750 [10],  MB#4749 [11],
MB#4791 [12]

Known issues

MB#4782 [13]: osso.Context causes segmentation fault
MB#4821 [14]: Cannot create HildonTouchSelector with single text column
MB#4824 [15]: python-mafw: source_browsing.py example does not work
MB#4839 [16]: python-mafw: mafw.Registry lacks list_plugins() method
MB#4849 [17]: python-mafw: MafwPluginDescriptorPublic structure is missing

We will not migrate to python2.6 in fremantle due to a (unresolved) bug (MB#4734 [18]), where a core SDK package explicitly conflicts with python >= 2.6, preventing any further upgrades from the 2.5.x series.

This release is supposed to be compatible with previous releases. If you have any issues regarding building your Python application on Fremantle, feel free to report it on the pymaemo-developers mailing list [19].

Acknowledgments

Thanks to everybody who helped making this release possible.

Bug reports, as always, should go to our Bugzilla [20]. Use the pymaemo-developers mailing list for help, feedback or suggestions.

References

[1] https://garage.maemo.org/projects/mafw/
[2] http://www.clutter-project.org/
[3] https://bugs.maemo.org/show_bug.cgi?id=4530
[4] https://bugs.maemo.org/show_bug.cgi?id=4450
[5] https://bugs.maemo.org/show_bug.cgi?id=4629
[6] https://bugs.maemo.org/show_bug.cgi?id=4628
[7] https://bugs.maemo.org/show_bug.cgi?id=4647
[8] https://bugs.maemo.org/show_bug.cgi?id=4632
[9] https://bugs.maemo.org/show_bug.cgi?id=4646
[10] https://bugs.maemo.org/show_bug.cgi?id=4750
[11] https://bugs.maemo.org/show_bug.cgi?id=4749
[12] https://bugs.maemo.org/show_bug.cgi?id=4791
[13] https://bugs.maemo.org/show_bug.cgi?id=4782
[14] https://bugs.maemo.org/show_bug.cgi?id=4821
[15] https://bugs.maemo.org/show_bug.cgi?id=4824
[16] https://bugs.maemo.org/show_bug.cgi?id=4839
[17] https://bugs.maemo.org/show_bug.cgi?id=4849
[18] https://bugs.maemo.org/show_bug.cgi?id=4734
[19] https://garage.maemo.org/mailman/listinfo/pymaemo-developers
[20] https://bugs.maemo.org/enter_bug.cgi?product=PyMaemo

Credits

This post was possible thanks to Anderson Lizardo, from PyMaemo team, who posted these informations on pymaemo-developers mailing list.

Introduction

As I promised in the preceding post, I'll provide a very easy example of a python binding. Let's suppose we don't want to use the methods included in Python to sum two integer values and we want to do it in C and then call the add method from a python script. I'll write the complete source code first and then I'll explain all the parts of it.

Source Code

#include <Python.h>

static PyObject *foo_add(PyObject *self, PyObject *args)
{
	int a;
	int b;

	if (!PyArg_ParseTuple(args, "ii", &a, &b))
	{
		return NULL;
	}

	return Py_BuildValue("i", a + b);
}

static PyMethodDef foo_methods[] = {
	    { "add", (PyCFunction)foo_add, METH_VARARGS, NULL },
	    { NULL, NULL, 0, NULL }
};

PyMODINIT_FUNC initfoo()
{
	    Py_InitModule3("foo", foo_methods, "My first extension module.");
}

How it works

First of all we have to include Python.h in our C file. This allows us to write an extension for Python language. To be able to include this header, we must have the python development packages installed in our system. For example in Debian based distributions we can install them with this command:

sudo apt-get install python2.5-dev

Every module has at least three parts. In the first part we write methods we want to call from the final python module: in this case we have a method called foo_add where "foo" is the name of the module and "add" the name of the method. Every method is declared as static PyObject. The method does anything particular except calling PyArg_ParseTuple to validate the input (we'll discuss this later), adding the two passed numbers and returning the result.

In the second part we have something like a dictionary, defined as static PyMethodDef and called foo_methods (where "foo" again is the name of the module). For each method we want to expose in our python module, we have to add something like this:

{"add", (PyCFunction)foo_add, METH_VARARGS, NULL}

where "add" is the name of the method we want to be visible in our module, (PyCFunction)foo_add is a pointer to our foo_add method, implemented in the C module, METH_VARARGS means that we want to pass some parameters to the function and the last one would be the description of the method (we can leave it NULL if we want).

Third part allows us to register the defined method/s and the module:

Py_InitModule3("foo", foo_methods, "My first extension module.");

Parsing Parameters

The PyArg_ParseTuple function extracts arguments from the PyObject passed as parameter to the current method and follows almost the sscanf syntax to parse parameters (in this case we had "ii" for two integers). You can fin the complete reference here: http://docs.python.org/c-api/arg.html

Building and installing

To build the module, we have to be in the source directory and execute this command:

gcc -shared -I/usr/include/python2.5 foo.c -o foo.so

then we've to copy the generated module to the python's modules directory:

cp foo.so /usr/lib/python2.5/site-packages/

Testing our module

Testing the module is really easy. We've to start a python shell or create a python script with the following source code:

import foo
print foo.add(2, 3)

if all is working fine, the printed result should be 5

References

• http://docs.python.org/extending/extending.html
• http://www.wrox.com/WileyCDA/WroxTitle/productCd-0764596543.html

MAFW is a new multimedia framework that will be used in Fremantle.

The PyMaemo team is currently working on writing bindings for Python
language for this library and at the moment we've released a 0.1
version of python-mafw that you can install directly from Scratchbox
repository.

Not all the methods are implemented (you can manage the Registry and
the Playlist, but nothing more), because even if we're using codegen
to generate bindings (and it's helping us a lot), we've seen that at
least 30-40 methods have to be overridden by hand so it's taking us
more time than we expected and we're trying to organize how to
continue this work.

We would like to get feedback from python application developers and
also from C application developers that are currently using MAFW so we
can work on a "roadmap" that reflects what developers want:

• What are the functionalities you're using in your application that you think they cannot miss in the Python binding?
• Have you already started using MAFW or even better python-mafw to develop something?
• What is the currently missing method/methods you would like to be implemented first?

Come on developers! We're waiting for your feedback

This summer I'm having the pleasure of working in Igalia (a spanish free software company) for a couple of months and they assigned me to an interesting project: developing Python bindings for MAFW library (a Maemo multimedia library that will be used in Fremantle release).

Having the opportunity to work both with C (yes, Python bindings are almost C code) and Python (it's a good practice to write unittest of all implemented methods) it's a good way to improve my knowledges in both languages and since I wasn't able to find much documentation about these kind of things, I'm going to share my own experiences.

What is a Binding?

A binding is a Python module, written in C language, that allows Python developers to call functions from existing C libraries from their python applications. It's just like a "bridge" from C world to Python one.

Why writing bindings?

There are a couple of reasons to write python bindings instead of writing a library in python language from scratch.

First of all I don't think is good duplicating code, so if a library already exists and it's written in C, why writing it again in another language? There's no reason. A lot of code already exist in C world and all we have to do is to create a bridge with python world.

Another good reason, in particular when a C library doesn't exist yet, is the fact that python code is slower than C code for some tasks (for example multimedia codecs). In these cases is good to implement the core library in C language and then create a python binding for it.

Coming next

As the title of this post says, this is only an introduction to the subjects I'm going to write about. If you have any particular request about any argument you would like to read, please feel free to leave me a comment. Next posts will talk about these things:

• A simple example of binding: I'll write a simple library in C language and I'll show how to create the relative python binding, providing complete source code and an example for python developers.
• Building and installing python bindings with distutils: I'll explain how to use distutils to build and install the binding (using the well know method "python setup.py install").
• Defining new types: this post will be about how to write new types in C language and being able to use them from python code.
• Using codegen to write bindings: I'll explain how to use codegen utils to automate lot of tasks, to generate the most part of binding code and how to customize the generated code using overrides.

This summer I'm working for 2 months at Igalia, a spanish free software company, and they assigned me the project of writing a Python binding for MAFW (a new multimedia library that will be included in Freemantle).

After few days I discovered that PyMaemo team was already working to it, so I asked to join them and they accepted me!

I really love Python language and since I think other developers love it too, I think we should provide good bindings for every library available in Maemo, so lot of developers can start writing their applications in this language.

I'll work to this project full time until the first week of september, so I hope to be able to learn a lot and to contribute as much as I can to this project.

If anyone else want to join PyMaemo team and help us to develop Python bindings, I think he will be welcome!

Paul Ferrill has written a serie of three articles about writing a GPS-aware application for the Nokia N810, using the Maemo SDK, Eclipse and PluThon plugin.

Here is the complete serie:

• Develop a GPS-aware application for the Nokia N810, Part 1: Development environment: Learn how to configure a development environment targeted at the Nokia N810 Internet Tablet, including setting up Eclipse on a target development machine for the Python language.
• Develop a GPS-aware application for the Nokia N810, Part 2: Consider your options: Discover the details of code design, library selection, unit testing, and user interface choices that make the most sense for you.
• Develop a GPS-aware application for the Nokia N810, Part 3: Finish the job: In this last of three installments, you'll put the final touches to the GPS trip tracker and get it ready for release.

Se abbiamo dei file audio in formato .wma e li vogliamo convertire in formato .mp3 utilizzando Linux, è sufficiente creare un piccolo script in bash che facendo uso di mplayer e lame provveda a convertire tutti i file che si trovano all'interno di una certa directory.

Creiamo un file chiamato wma2mp3.sh con all'interno il seguente script:

#!/bin/bash

rm audiodump.wav


a questo punto basta mettere lo script nella cartella dove ci sono i file .wma, dare i permessi di esecuzione a tale file (chmod +x wma2mp3.sh) ed eseguirlo con ./wma2mp3.sh

Fonte: http://www.linuxquestions.org/linux/answers/Applications_GUI_Multimedia/Convert_WMA_to_MP3