Bullet on my own foot: trying to uninstall Python 2.6 from Ubuntu 9.10 Karmic Koala

Some major Linux distros use Python for maintaining their packages. Red Hat (and its downstream distros) which use the yum tool uses Python 2.4. I tried to install Python 2.6 in CentOS 5.4 without success. The tool rejected to install Python other than 2.4 using that tool out of fear that it will interfere with the tool.

I just found another catch, when you are trying to install Python 2.6 in Ubuntu (I was using Karmic Koala, 9.10), such as:
[source lang='shell']
$ sudo apt-get remove python2.6
[/source]

It will display the components that are about to be removed.
Kids, don't try this at home!
It will remove your whole desktop related application! Java, Gnome, apt tools. You practically will be left with command line Linux, and without the apt tools.

Uninstalling Python 2.6 from Ubuntu seems to be an act of shooting own's foot!

Lucky I tried on not-so-important experimental Ubuntu installation on my laptop.

Again about Google DevFest 2010

Yesterday I had to leave an hour earlier from the Google DevFest 2010 event, as I have to  catch up with my wife, she was waiting for me for the second Antenatal Class. I missed the Code Lab, the Maps and Buzz T-shirts. Ouch. 5:30pm I had to leave while they ended the event on 6:30pm.

Flash back: After lunch time, there were some presentations on Google Apps, by Patrick Chanezon, followed by success story of people who developed applications for Google Apps. One from creately.com (http://www.creately.com). Another round from SingPath (http://singpath.appspot.com).

One thing that was missed a lot is the power points (aka power plugs). It was awful so many people carrying laptop and no power plug on the Connexis Theater. Almost everyone were running out of battery.

I just don't know why the crowd was kinda lacking enthusiasm to verbally respond to the speaker on stage with 'ooo's, 'aaaa's, 'yeah's, 'alright's and stuffs. Most of the time the crowd was silent.

Nevertheless it was a must-attend event of this year. I will attend the next event for sure.

 

In Google DevFest 2010

Currently I am attending the Google DevFest 2010. Timothy Jordan and Bob Aman in their presentation on Open Social.

Today the registration was pretty crowded, and they differentiate based on the first letter of your first name. I was in the "A-F queue". The queue was long and the registration process was draggy.

They changed the schedule a bit, Daniel Lee presented the Google Maps as opposed to the initial schedule on the web site: Google DevFest 2010 in Singapore. He showed us how to create a coffee shop location based informative web site as an example.

After the first session, Jeremy Orlow, an engineer working on the Chrome team, explained the HTML5 and the Chrome. They skipped the Q&A for HTML5 and Chrome. May be they pushed forward because we're late because of the registration, so in order to finish during the lunch time, the organizer advised to ask in person to Jeremy during lunch time for anyone who want to ask questions.

Then here comes the third session, and its about  Open Social.  Tim was of more lively presenter than others I think. More like MC may be? Google Buzz API stuffs, atom, OAuth, Salmon, Pubsubhubbub etc.

PyDev 1.5.8 is out: Eclipse IDE + PyDev == Cool Python IDE

PyDev 1.5.8 is out now. Eclipse update site: http://pydev.org/updates

• Support for Eclipse 3.6 Helios
• The PyDev jar is not signed out (no more confirmation message that you are installing from untrusted source during the Eclipse plugin installation)
• DoesNotExist and MultipleObjectsReturned recognized in Django
• Some issues fixed

PyDev is a plugin that enables users to use Eclipse as an IDE for Python, Jython and IronPython development. It has the syntax highlighting, refactor, syntax analysis, debug, and code completion.

Mercurial Server 1.0.1 Installation on Ubuntu

When we are working using Subversion, we can expose the Subversion repository using svnserve (open the default port 3690 and svn:// protocol) or leverage the Apache WebDav to expose your Subversion service in HTTP (the web protocol -- I've always tempted to write it as HTTP Protocol which is incorrect as the last P letter stands for 'protocol').

And of course if you are just as lazy as I, you will use the CollabNet Subversion or Edgewall Trac.

Mercurial Server from Lshift is one way to achieve similar thing. Though it is named Mercurial Server, it is not a server in traditional client/server perspective. It leverages the SSH authentication to make it like a central repository where multiple user can access and serves the same purpose.

Surprisingly, it is very easy to install in an Ubuntu box.

[sourcecode lang="shell"]
$ sudo apt-get install mercurial-server
[/sourcecode]

Gotcha! You have it now.
With this Mercurial Server, you can access the server using:
hg clone ssh://<ssh-user>@<host-name-or-ip-address>[:<ssh-port-num>]/<folder>

[sourcecode lang="shell"]
$ hg clone ssh://mercurial@192.168.0.1/projects
[/sourcecode]

Attending Singapore Google Technology Group Meetup

 

Today I attended this Singapore Google Technology User Group Meeting. It's my first time to attend such a Google meetings. Some of previous meet ups had always fallen on the wrong days -- on the day that I have something else to do. Today I am glad to be able to make it, attended the meeting, and Wesley Chun, was the speaker. He presented 2 sessions, one about Python and the other one about Google App Engine.

This guy's a hardcore Python guy, wrote the Core Python series of book, and was a presenter in the PyCon Asia Pacific 2010, Singapore -- an event that has been held last 3 days. Awesome in depth knowledge, vast industrial experiences, and keep the talk flows fluent.

The rest about the meeting can be found here: http://www.sg-gtug.org/2010/05/sg-gtug-special-tutorial-session-june.html

Playing with IronPython again

It's been quite a while I haven't posted anything on this blog. I was too lazy to write. Now that I regain the composure, try to write again.

I have tried IronPython 2.6 before. It was presented in Python User Group Singapore somewhere last year which captured my attention. The IronPython made it easy to play around with .NET and Silverlight stuffs -- which not easy for me as I haven't play with .NET stuffs for quite sometime. It worked well that time. Recently when I want to run the ipy.exe interpreter, I came into certain problem. I was running it on Vista box, but the application crashed after I started, after around 30 seconds waiting for nothing. I try to do some ordinary "dance" like unistall-install, with no luck.

Today I gave it a try again, and eventually it worked after I installed the .NET framework 4 and Silverlight 4 from the download site. I wasn't sure what I missed, nevertheless now it works.

I tried some stuffs with Silverlight only to remind that I need a XAML editor to edit forms. I tried to download and use kaxaml from http://www.kaxaml.com, but haven't had much luck. It installs well, but didn't run quite well.

PyCon Asia Pacific 2010 has been firmly announced

Now they announce the PyCon Asia Pacific 2010.

http://apac.pycon.org/

9-11 June 2010, at Ngee Ann Kongsi Auditorium, Singapore Management University.

SGD 250 for corporate.
SGD 200 for early bird individuals.

Highlights:

• Steve Holden, Chairman of the Python Software Foundation (PSF) will be coming  as one of the keynotes
• Mark Hammond, author of "Python Programming on Win32"
• Wesley J. Chun, author of "Python Core Programming", now software architect at Google
• Martijn Faassen, a long standing member of the Zope Foundation

Missed PUG monthly meeting, exploring Java byte code and BCEL

I missed yesterday's Python User Group Singapore monthly meeting. I had to finish certain document before leaving office yesterday, I couldn't make it.

Last night I was exploring this Byte Code Engineering Library (BCEL) from Apache. This library gives us a way to analyse, create and manipulate binary Java class file. This library has been used by a lot of Java frameworks and containers, as those frameworks need to add some instrumentation when deploying those components in those frameworks and/or containers.

Well, this is considered an advanced thing in Java. Java classes are stored as Java byte codes. When you compile a Java source code, you will have .class file which is a Java byte code file. Java byte code is a form of machine instruction (in this case Java Virtual Machine or JVM). So it's executable binaries for JVM. Java byte code also have opcode like assembly language.

There are 2 type of instruction sets:

1. stack machine
2. register machine

Stack machine operates on stack. Operands are the stack only. The first programmable scientific calculators released by Hewlett-Packard are stack machines (http://www.hpmuseum.org/). They operate in a Reverse Polish Notation. I remembered that my first one of my first Java programming assignment was to implement GUI application for a Reverse Polish Notation calculator. My Dad has his own story of owning one of these calculators and he used to be very proud of the magnetic stripe stored Moon Lander game. It's just a number only Moon Lander, but it's a game running on programmable HP calculator!

Other sample of stack machines that most of us still use is the Intel x86 math coprocessor instructions set. It uses registers that are organised as stack, which will rotate back when overflowing the boundary (of 8 registers).

Stack machines, because it's only operate on stack and usually only the last few data in stack, may have shorter instruction bits. Unlike register machines which usually take some of the bits to specify from which and which register the data is from, and to which register the result goes, stack machines enjoy the benefit of default operands, that is top 1 or top 2 of the stack. The result is always in the stack.

I think one of the main considerations why JVM uses stack machine is to pack as few numbers of bits in the opcode. As most JVM runs as virtual machine, there will be no performance advantages of having a lot of register which anyway stored in RAM by the virtual machines.

Ok, enough for the stack machine, now back to the BCEL it's exciting to touch back the assembly language, byte code, opcode, operand, and stuffs if you are really into  it. I try to code a bit and will share the code later.

What is Spring Python?

Spring Python takes the concept of the Spring Framework and applies them to Python. This means that we can take advantage of the features of Spring Framework such as Dependency Injection (Inversion of Control), aspect oriented programming (AOP), remoting, data access, transactions, and security, all with the same non-invasiveness style.

This means that:

• it will be easier to unit test software components (Python objects with standardized dependency injection)
• we can move cluttering code outside the object and have cross-cutting functionalities (aspect oriented programming)
• scalability of business objects by adding remoting
• transaction (ACID)
• security (interceptor based which won't allow outside world to touch your application unless they are really authenticated an authorized)
• you don't have to extends certain class in order to get all those features (non-invasiveness)

The project was started independently by Greg L. Turnquist, which later joined the SpringSource team as Project Lead for Spring Python project. He also authored "Spring Python" book from Packt.

Spring Python is now approaching version 1.1 with its second milestone before release 1.1.0.M2. Current stable release version is 1.0.0.

All about SpringPython can be found on its web site http://springpython.webfactional.com/

PyDev 1.5.6 has been released

PyDev is a plugin that enables users to use Eclipse for Python, Jython and IronPython development -- making Eclipse a first class Python IDE -- It comes with many goodies such as code completion, syntax highlighting, syntax analysis, refactor, debug and many others.

Fabio Zadrozny from Aptana, the author of PyDev plugin,  passed this information through mailing list:

This Release Highlights:

• Django integration:

• 
  
  
  
  • New Django project can be created through twizard
  
  
  • Can set an existing porject as a Django project (right-click project > pydev > set as django project) I think this is a kind of Eclipse's personality, like those of Maven2 plugins where you can declare that this project is a  Maven project
  
  
  • New Django project can be created throughtwizard
  
  
  • Can remove Django project config (righ-click project > django > remove django project config)
  
  
  • Custom actions can be passed to the configured manage.py through ctrl + 2 + dj django action -- if not action is passed, will open to choose from a list of previously used command
  
  
  • Predefined/custom actions can be used through right-clicking the project > django > select custom action
  
  
  • manage.py and settings module configured
  
  
  • Django shell (with code-completion, history, etc) available
  
  
  • Run/Debug as Django available
  
  
  • See: http://pydev.org/manual_adv_django.html for more details
  
  
  
  

• Find/Replace:
  
  
  
  • The search in open files is no longer added in the find/replace dialog and now works through Ctrl  + 2+  s word_to_find (in the PyDev editor) and if no word is passed, the editor selection is used
  
  
  
  

• Go to definition:
  
  
  
  • Properly works with unsaved files (so, it will work when searching for a definition on an unsaved file)
  
  
  • Properly working with Eclipse 3.6 (having FileStoreEditorInput as the editor input)
  
  
  
  

• Editor:
  
  
  
  • Automatically closing literals
  
  
  • Removing closing pair on backspace on literal
  
  
  • Improved heuristics for automatically closing (, [ and {
  
  
  • Removing closing pair on backspace on (, [ and {
  
  
  • Ctrl + 2 + sl (sl comes from 'split lines' -- can be used to add a new line after each comma in the selection
  
  
  • Ctrl + 2 + is (is comes from 'import string' -- can be used to transform the selected import into a string with dots
  
  
  
  


• General:
  
  
  
  • Code-completion properly working on relative import with an alias
  
  
  • Fixed racing issue that could deadlock pydev (under really hard to reproduce circumstances)
  
  
  • Removing reloading code while debugging until (if) it becomes more mature in the python side
  
  
  • Fixed issue where a new project created didn't have the source folder correctly set
  
  
  • Text selection in double click no longer has weird behavior
  
  
  • Local refactoring working on files not in the PYTHONPATH
  
  
  • Edit properly working on string substitution variables
  
  
  • Using with statement on python 2.5 no longer makes lines wrong in the AST
  
  
  
  

Playing around with Ordered Dictionary (collections.OrderedDict)

The new and cool feature added to Python 3.1.x family is the Ordered Dictionary. Some implementations have been lying around for sometime, it's good to see one made it into  the Python standard library.

Dictionaries are general purpose container data structure that are accessed through keys. It uses a hashing mechanism to achieve fast retrieval of information by key on typical cases. The annoying thing about standard dictionary dict object is that, whenever we retrieve the keys, it is not guaranteed to be sorted.
In Java platform, usually this dictionary is called map. java.util.Map provides interface to implementations of map such as java.util.HashMap, java.util.TreeMap.

Every value is associated with value, written in : pair.

Try to paste this code to your Python 3.1 interpreter:

[sourcecode lang="python"]<br />ud = dict()<br />ud['c']='1'<br />ud['b']='2'<br />ud['a']='3'<br />[/sourcecode]

This interactive session below highlight the thing:

[sourcecode lang="shell"]<br />>>> ud = dict()<br />>>> ud['c']='1'<br />>>> ud['b']='2'<br />>>> ud['a']='3'<br />>>> ud<br />{'a': '3', 'c': '1', 'b': '2'}<br />[/sourcecode]

Nice general purpose container for all of our applications. The dictionary keys doesn't display in sorted order.

Instead when we paste this code into Python interpreter:

[sourcecode lang="python"]<br />import collections as coll<br />od = coll.OrderedDict()<br />od['c']='1'<br />od['b']='2'<br />od['a']='3'<br />[/sourcecode]

We will get this result:

[sourcecode lang="shell"]<br />>>> import collections as coll<br />>>> od = coll.OrderedDict()<br />>>> od['c']='1'<br />>>> od['b']='2'<br />>>> od['a']='3'<br />>>> od<br />OrderedDict([('c', '1'), ('b', '2'), ('a', '3')])<br />[/sourcecode]

As we can see in the result above, the collections.OrderedDict objects displayed the keys according to the sequence that they were inserted. When an insertion done on an already existing key, the new insertion will overwrite the value but the sequence is left untouched. A deletion followed by addition will move the key to the end of the list, as show in the session below (continuation of the previous one).

[sourcecode lang="shell"]<br />>>> od['d']='4'<br />>>> od<br />OrderedDict([('c', '1'), ('b', '2'), ('a', '3'), ('d', '4')])<br />>>> od['b']='5'<br />>>> od<br />OrderedDict([('c', '1'), ('b', '5'), ('a', '3'), ('d', '4')])<br />>>> od.pop('a')<br />'3'<br />>>> od<br />OrderedDict([('c', '1'), ('b', '5'), ('d', '4')])<br />>>> od['a']='6'<br />>>> od<br />OrderedDict([('c', '1'), ('b', '5'), ('d', '4'), ('a', '6')])<br />>>><br />[/sourcecode]

I guess "battery included" still holds, or probably, "more organised battery included...".
Hooray for Python.

Python 3.1.2 Released (bug fix released)

Python 3.1.2 (bugfix release) is out now! We can download from this site: http://www.python.org/download/

Spring Python 1.1.0.M1 Released

SpringSource has has just announced last  week of a milestone release of SpringPython 1.1.0.M1. This announcement made aware about this project. There is a project that has nearly reached its 1.1 version that tries to develop Spring-like framework in Python. I would like to look into this project.

It is different from invoking Spring Java from Jython in  that, this project brings the concept of Spring framework into the CPython platform in general. Some of the configuration are really Pythonic!

I think I will explore more on this project.