Using IPython in your Python Codes

After a while, I thought I should jot this down for anyone who might want to write a certain kind of python script, where they may want to keep the code cached for a significant duration. One of the best tools for this is IPython.

For those familiar with python programming, IPython needs no introduction. I will forgo the niceties and just cut to the chase for the uninitiated. IPython is a python framework which provides an interactive real-time programming experience for the users. It is complete with an interactive shell, a QT graphical user interface and a web interface; the infamous IPython Notebook. Installation guides are all around the web so a simple Google will do.

However, imagine a situation where you have certain piece of code running, say, a server (take Tornado or Django for instance). And you want to run your python codes in a dynamic manner; you want to create  a variable during breakfast, and want to use it as a count for your web-site's visitors, and during lunch, you want to check how many visitors have come to your site. One approach will be to go full caveman and keep a thread running in the background and, is there anything we hate more than dealing with implementing a running thread with an interactive interface?

IPython provides a simple, elegant solution for this. You can initiate a 'kernel' of IPython, and the kernel will act as a single, independent and contiguous runtime instance for Python. Imagine the possibilities with this. However, harnessing the power of this extremely useful tool is not easy for a beginner with the lack of detailed documentation, for understandable reasons.

Now for the fun part; There is only one class that you have to import in your code to do this (note that I assume you already have IPython framework installed in your computer). That is the "KernelManager" object provided in IPython. I'll boil it down to the simple steps you have to follow.

1. Create a Kernel Manager
2. Use the Kernel Manager to create a kernel instance and run it
3. Use the Kernel Manager to create a client which communicates with the said kernel
4. Open a channel between the client and the kernel using the client (four kinds of channels, go through the documentation for detailed information on them)
5. Feed your code through the ShellChannel of the client. 

The Sample code looks something like this. 

from IPython.kernel.manager import KernelManager

km = KernelManager()

km.start_kernel()

cl=km.client()

chan = cl.shell_channel()

code_str= "f = open ('/home/yourname/yourfile.txt','w')\

f.write('the sample works')\

f.close()"

chan.execute(code_str)

et voila.... You have a code!

If you need any clarifications, please ask below. Have an interview. Gotta go...