Python for Girls!

Hi all! I'm working on a new python tutorial for beginners, specifically aimed at girls. There aren't many of those out there yet, so I thought it would be a great opportunity to help start building the library! Here's a link to my documentation so far: http://docs.google.com/View?docID=0AQGjCIWYc3RlZGdoYjk0bnRfMTQwMmNtcTVrNmhm&revision=_latest&hgd=1. It's definitely a work in progress, but feel free to peruse the tutorial. If you notice any errors, feel free to comment!

What I think sets this tutorial apart from the rest is the writing style and approach to teaching. I'm writing the tutorial in a very comfortable and relaxed voice. I write what I would say if I was explaining python to someone in person, interjections and all. Hopefully this will make the tutorial more interesting and easier to read.

My approach to teaching is also different in that I provide concrete examples before explaining the programming concept. From what I've read (sorry, can't find the post anymore..), girls learn programming better when they first understand the problem at hand, then are taught how to solve the problem. I use this format frequently in my tutorial. For example, I first ask how lists are used in real life and provide some examples before even explaining what a python list is. This will hopefully help the girls realize that programming is about solving real life problems, such as creating the list of TV shows to display in the TiVo menu or creating an application to track your grocery list, and then teach them how to do so.

I'm hoping this approach will work well! I get a chance to test my material at the Summer Enrichment Program! If I have time, I will try to document my experience (what worked, what didn't) so that future tutorials can continue to improve!

Android Unboxing

Having fun with Android today:

Creating an Android 'Library'

In some instances, you might want Android classes available to multiple Android applications. To simply add an Android project to the another Android project's build path will not work (a good explanation is here: http://groups.google.com/group/android-developers/browse_thread/thread/5537ae10e4143240). A workaround is summarized below:

1. Create a new Android project.

2. Add any necessary classes and interfaces (including AIDLs)

3. Allow the AIDLs to compile and generate Java code.

4. Update the .project file. This file is located in the root of the Android project. It contains the following contents:

1:  <?xml version="1.0" encoding="UTF-8"?> 
2:  <projectDescription> 
3:  <name>[project name]</name> 
4:  <comment></comment> 
5:  <projects> 
6:  </projects> 
7:  <buildSpec> 
8:  <buildCommand> 
9:  <name>com.android.ide.eclipse.adt.ResourceManagerBuilder</name> 
10:  <arguments> 
11:  </arguments> 
12:  </buildCommand> 
13:  <buildCommand> 
14:  <name>com.android.ide.eclipse.adt.PreCompilerBuilder</name> 
15:  <arguments> 
16:  </arguments> 
17:  </buildCommand> 
18:  <buildCommand> 
19:  <name>org.eclipse.jdt.core.javabuilder</name> 
20:  <arguments> 
21:  </arguments> 
22:  </buildCommand> 
23:  <buildCommand> 
24:  <name>com.android.ide.eclipse.adt.ApkBuilder</name> 
25:  <arguments> 
26:  </arguments> 
27:  </buildCommand> 
28:  </buildSpec> 
29:  <natures> 
30:  <nature>com.android.ide.eclipse.adt.AndroidNature</nature> 
31:  <nature>org.eclipse.jdt.core.javanature</nature> 
32:  </natures> 
33:  </projectDescription> 

Remove the following elements from the buildSpec:

1:   <buildCommand>  
2:  <name>com.android.ide.eclipse.adt.ResourceManagerBuilder</name>  
3:  <arguments>  
4:  </arguments>  
5:  </buildCommand>  
6:  <buildCommand>  
7:  <name>com.android.ide.eclipse.adt.PreCompilerBuilder</name>  
8:  <arguments>  
9:  </arguments>  
10:  </buildCommand>  
11:  <buildCommand>  
12:  <name>com.android.ide.eclipse.adt.ApkBuilder</name>  
13:  <arguments>  
14:  </arguments>  
15:  </buildCommand>  

Remove the following element from the natures:

1:   <nature>com.android.ide.eclipse.adt.AndroidNature</nature>  

5. Save the updated .project file.

6. Refresh the Android project in Eclipse.

7. Clean the project (select the project folder, select Project > Clean... from the main menu)

8. Remove the R.java file from the generated files.

Your project should now be ready to be added to the build path of other Android projects.

Updating sqlite database from the command line - django

I'm working with django today and realized halfway through that my database was incorrect. I needed to drop columns from a table and create a new table. The syncdb command, from what I've read, does create new tables, but it will not drop columns. So, I had to directly access the sqlite database from the command line. Luckily this is pretty easy. Just navigate in the Terminal window to the directory where the database file is saved. Then run the following command:

sqlite3 [database filename]

This will start sql in the Terminal window. From here, you can run the typical sql commands to select rows, update rows, etc. In my case, I simply dropped all tables so I could start from scratch:

DROP TABLE search_searchresult;

This could be a very useful for other problems, such as uploading bulk data.

Google App Engine - printing debug messages

The logging.debug statements are not printed by default in the local development server of Google App Engine projects. In order to display these messages, you need to add the "--debug flag" to the launch settings. Here are the steps to do so:

1. Open GoogleAppEngineLauncher
2. Right-click on your app engine project
3. Select Info...
4. In the Launch Settings section, enter "--debug" in the Extra Flags box.
5. Click Update.

Restart the server. The Logs should now display DEBUG statements in addition to warnings and info.

Unzipping jar files

Wow, opening jar files is much easier than I realized! I had been expanding them from the command line for a couple years now. Today, I just found this page: http://ostermiller.org/opening_jar_files.html. All I have to do on my Mac is change the extension to .zip and double click. Wow.

Installing rdflib - Mac OS X 10.5.8

Installing rdflib seems easy enough, but I ran into a couple of weird issues that were not documented anywhere online. I wanted to share my experience in case anyone else ran into these same problems!

First, I tried the easy_install command recommended by the site. This was the output I received:

Searching for rdflib==2.4.2
Reading http://pypi.python.org/simple/rdflib/
Reading http://rdflib.net/
Best match: rdflib 2.4.2
Downloading http://rdflib.net/rdflib-2.4.2.tar.gz
Processing rdflib-2.4.2.tar.gz
Running rdflib-2.4.2/setup.py -q bdist_egg --dist-dir /var/folders/Lr/Lrriod8lEEm63-sPBZf6XE+++TI/-Tmp-/easy_install-xa0EVw/rdflib-2.4.2/egg-dist-tmp-qvivjK
warning: no files found matching 'example.py'
zip_safe flag not set; analyzing archive contents...
No eggs found in /var/folders/Lr/Lrriod8lEEm63-sPBZf6XE+++TI/-Tmp-/easy_install-xa0EVw/rdflib-2.4.2/egg-dist-tmp-qvivjK (setup script problem?)

Uh, no egg found? I suppose that's somewhat appropriate, it is Easter today (darn Easter bunny!). I didn't think I could easily solve this problem, since there might be a problem with the setup script.

So, I tried downloading the tar file. Upon unpacking the file, there was a setup.py file. Great! I just need to run python setup.py install, right? Wrong.. here's the output:

Traceback (most recent call last):
File "setup.py", line 1, in
from setuptools import setup, find_packages
ImportError: No module named setuptools

OK, I checked the directory again, and noticed that there was an ez_setup.py file. Maybe this would do the trick? I ran python ez_setup.py, and there were no errors! Here was the output:

Downloading http://pypi.python.org/packages/2.5/s/setuptools/setuptools-0.6c9-py2.5.egg
Processing setuptools-0.6c9-py2.5.egg
Copying setuptools-0.6c9-py2.5.egg to /Library/Frameworks/Python.framework/Versions/2.5/lib/python2.5/site-packages
Adding setuptools 0.6c9 to easy-install.pth file
Installing easy_install script to /Library/Frameworks/Python.framework/Versions/2.5/bin
Installing easy_install-2.5 script to /Library/Frameworks/Python.framework/Versions/2.5/bin

Installed /Library/Frameworks/Python.framework/Versions/2.5/lib/python2.5/site-packages/setuptools-0.6c9-py2.5.egg
Processing dependencies for setuptools==0.6c9
Finished processing dependencies for setuptools==0.6c9

Looks like this solves the earlier error I received when running python setup.py install: the setuptools package was created! Great! I ran python setup.py install again, and rdflib was successfully installed...

with one caveat: the build files are located in build > lib.macosx-10.3-fat-2.5 (or some similar directory) > rdflib. Make sure to put this path in your PYTHONPATH. So far, I found one file in here that is necessary for running SPARQL queries, SPARQLParserc.so. It's not in the rdflib directory at the root of the rdflib-2.x.x directory!

Good luck!