01 February 2014

Two days ago I looked for a good project to partecipate with the purpose of enhancing my skills about writing good alghoritms. So I moved my very first steps searching a good starting point in this matter; as a gift of the holy fate I received a mail from coursera reminding me the forthcoming of a new session of the Algorithms I course by the Princeton University College, but this is not what I was looking for, at least not completely. For the gods sake I then recalled the presence of an unfinished project of my friend @origama, here on GitHub, under the Zencoders group (read the manifesto and feel free to take part). This project moved from the original idea of @etr to make a set of libraries in C++.

I do not know C++ programming language, so I opted for algoritmica.sh, wich is no less than a parallel project conceived in Bash. I then decided to drag in this endavour, encouraged by the possibility of using these experiments shortly afterwards in an upcoming project. With the best expectations I started studying the code made by origama, but a soft voice from my soul was suggesting to stop and choose another way («follow the force» and «use a Jedi technology» were the recurring phrases). Then I bumped into this:

[…] let’s get away from the nonsensical scripts and actually write something useful. Python has a massive standard library that can be used by simple importing modules.

I suddendly realized that the right way was Python. So here the real story starts. I resumed this doc page but the highlighted message in red on the top of that page redirects me on argparse, rather than optparse. My problem on that precise moment? I use Ubuntu 10.10 as my operating system and I have Python 2.6: I should have to install the new version of the interpreter… There was also an alternative by using a virtualenv

 virtualenv --python=/usr/bin/python2.7 algopy

Why virtualenv?

The basic problem being addressed is one of dependencies and versions, and indirectly permissions. Imagine you have an application that needs version 1 of LibFoo, but another application requires version 2. How can you use both these applications? If you install everything into /usr/lib/python2.4/site-packages (or whatever your platform’s standard location is), it’s easy to end up in a situation where you unintentionally upgrade an application that shouldn’t be upgraded.

Eriol, from the Catania GLUG, pointed me in the right direction suggesting to include a setup.py with the necessary dependencies and also to give a message to the user with a try-except on the import with an error message linking to https://pypi.python.org/pypi/argparse.

try:
     import argparse
except ImportError, e:
     sys.stderr.write(e)
     sys.stderr.write("You must install argparse: https://pypi.python.org/pypi/argparse")

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