Ruby on Rails versus Python
Ruby and Python have more similarities than differences; the same is true for Rails and Django, which are the leading web frameworks in the respective languages.
Both languages and both frameworks are likely to be rewarding to work with - in personal, "fun" terms at least - I don't know what the job markets are like in the specific areas.
There are some similar questions in StackOverflow: you could do worse than clicking around the "Related" list in the right-hand sidebar to get more feel.
Best thing is to get and try both: pick a small project and build it both ways. Decide which you like better and go for it!
I am in the field of data crunching and very soon might make a move to the world of web programming. Although I am fascinated both by Python and Ruby as both of them seem to be having every similar styles when it comes to writing business logic or data crunching logic.
But when I start googling for web development I start inclining towards Ruby on Rails my question is why is the web world obsessed with ruby on rails and active records so much?
There seem to be so many screencasts to learn Ruby on Rails and plethora of good books too 
why is Python not able to pull the crowd  when it comes to creating screencasts or ORM's like active record.