How to send the text pasted in a textbox of a html webpage to the application written in python in the harddisk?
Here's my suggestion: modify your program to include a button for doing the transformation. When you click it, it should take the contents of the clipboard, do whatever transformation you want, and put the result back on the clipboard.
Once you do that, to use it you select the text from the widget, use the keyboard to copy it to the clipboard, press the button on the GUI, then click back in the widget and use the keyboard to paste.
Alternately, your program can just poll the clipboard every couple of seconds, do the transformation and put the results back (make sure your automatic polling ignores any changes caused by itself). With that you can do a select-all, copy, wait a couple seconds, then paste.
This is pretty trivial to do in both Tkinter and wxPython, and I would guess it is equally trivial with most other GUI toolkits.
I have a application running in python, i want to send the input taken from the text box of the webpage and send it as input to the application and once again the output of the application which is in text format back to the result page on web. 
thanks a lot for your time :) :)