Writeable Foreign keys in Django Rest Framework

Mon 09 December 2013 by guglielmo
Filed under howto Tags python django django-rest-framework API

Django Rest Framework is a django-based framework to produce browseable APIs.

The documentation and the tutorial are pretty much clear, but implementing a writeable API for related fields can be tricky.

RelatedField is read-only. PrimaryKeyRelatedFields, HyperlinkedRelatedField, SlugRelatedField, can be used as writeable, but the related items must already exist. It seems they’re more appropriate to handle aggregation relations (i.e. User and Groups)

Nested relationships can be used to handle composition relations (i.e. a Place and its Acronyms). The quirk is that the get_identity() method must be re-written in the nested serializer, because the default one uses the id field to determine the identity of the items, which may not have, and which you surely don’t have when creating new items.

A working example with Places and Acronyms can be found here.

Given a Place instance with just one acronym, the JSON representation would be:

{
    "_self": "http://localhost:8003/maps/places/roma-comune",
    "slug": "roma-comune",
    "name": "Roma",
    "acronyms": [
        "RM"
    ]
}

PUTting the following json payload to the resource:

{
    "slug": "roma-comune",
    "name": "Roma",
    "acronyms": [
        "RM", "ROM"
    ]
}

or PATCHing the even shorter one:

{
    "acronyms": [
        "RM", "ROM"
    ]
}

The final result would be that the ROM acronym would be added to the Place resource.

Using Mapnik inside a virtualenv on OSX

Sun 20 October 2013 by guglielmo
Filed under howto Tags python osx macports

Mapnik is a tool to produce maps out of gis data.

Since installation in a virtualenv through pip install mapnik2 fails, due to compilation problems (boost library cannot be located correctly), the following workaround can be used.

Install Mapnik through macports:

sudo port install mapnik @2.2.0_0+python27

This ...

Using Tkinter inside a virtualenv

Sat 19 October 2013 by guglielmo
Filed under howto Tags python osx macports

Tkinter is usually installed on OSX trhough macports as a global package:

sudo port install py27-tkinter

Within a virtualenv the package will not be imported, as global packages are not included by default:

>>> import Tkinter
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/opt/local/Library ...

Fixing the “can’t start the AWT” bug for Tomcat6

Tue 25 June 2013 by guglielmo
Filed under howto Tags tomcat6 java macports osx

After a Java upgrade on the OSX, Tomcat6 is not starting properly. The log shows a Java error:

2013-06-27 14:45:40.300 jsvc[57146:203] Apple AWT Java VM was loaded on first thread -- can't start AWT.
Jun 27, 2013 2:45:40 PM org.apache.catalina.startup ...

How to configure bash completion in ubuntu

Thu 11 April 2013 by guglielmo
Filed under howto Tags bash terminal

Working almost always in the terminal of a linux box, the autocompletion feature enhances your speed and comfort, a lot.

Under Ubuntu, autocompletion is installable, if not already installed, with:

apt-get install bash_completion

The ~/.bashrc config file should contain these lines:

if [ -f /etc/bash_completion ] && ! shopt -oq posix; then
    . /etc ...

How to install solr on tomcat7, over Ubuntu 12.04

Wed 10 April 2013 by guglielmo
Filed under howto Tags solr tomcat ubuntu

Tomcat7

Ubuntu 12.04 comes with tomcat easily installable as a package (you need jdk):

apt-get install default-jdk tomcat7 tomcat7-admin tomcat7-user tomcat7-docs

Configure access to the web-admin in /etc/tomcat7/tomcat-users.xml:

<tomcat-users>
  <role rolename="manager-gui"/>
  <user username="manager" password="S3krEt" roles="manager-gui"/>
</tomcat-users>

The tomcat management console is now ...

OpenSource in the UK

Wed 20 March 2013 by guglielmo
Filed under reporting Tags politics open source

The UK government issued a beta version of the Service Design Manual, stating guidelines on how to design digital services according to the Digital by Default Service Standard.

Setting a digital service standard is part of the Governmental Digital Strategy, which aims at producing public digital services, “so good, that ...

Bureaucrats like Github

Fri 15 March 2013 by guglielmo
Filed under reporting Tags politics open source

A post on Oreilly Radar informs us that Github is trending as the social-repository of choice for governments and public institutions who want to publish data, standards and source code.

Some remarkable examples:

BLOG TODO LIST

Mon 17 September 2012 by danielef
Filed under posts

UPDATED by guglielmo Nov, 11th, 2012

refine blog deploy flow (make/fab file) - OK
make a theme - OK (sortof)
add links
disqus - OK
google analytics - not OK