Someone told me once, that programmers tend to learn one scripting language properly and ignore or dislike other scripting languages. Do you have similar experiences? I'm using Python as my choice for scripting for few years, however, I'm sure that there are many existing and emerging languages that could impress the Pythonistas. Can you recommend scripting languages that would be interesting and useful to learn besides of Python?
Look, Python pretty much has all you need (in my opinion) for application programming. You can write anything from a protocol stack to YouTube, from media players to 3D games and graphics and you get excellent performance.
It occupies the same niche as some of these other mentioned languages:
C, you have access to almost all of the useful C/C++ libraries. The only reason I would pick to write something in C over Python is because I needed the performance gain. Even then, I would probably prototype it in Python first; it's much easier to revise your design when your application is written in Python.
Ruby, there is no good reason to ever use Ruby instead of Python.
Perl, it's great for some particular kinds of tasks, but if you're a fan of consistent, readable and sane programming styles you will hate looking at about 95% of existing Perl code. I don't know if this is because the people who program in Perl tend to be (in my experience) sys admins first and programmers second, or because Perl has a design philosophy that allows for multiple distinct ways to achieve the same effect.
Given that, I would say that if you are going to learn another language, make sure it gives you the ability to do something new. There are two scripting languages that I would recommend for you to learn:
Bash, what a joy it is to manipulate your filesystem with a combination of for loops and pipes. Bash programming doesn't give you more than what you can already do with Python, but if you are a *nix user you will experience great gains in your daily productivity.
Javascript, being able to write browser-based applications is a useful skill and almost definitely the way most applications will be done in the future. The Javascript/browser environment is set to gain a whole host of capabilities in the coming few years, from audio manipulation to OpenGL graphics, and some very fast engines are either in the works or already available (like V8, which powers the Chrome browser and compiles Javascript to native byte code.) Have you seen Quake2 ported to WebGL?
My answer basically boils down to this: first, learn languages that are useful.