I'd go with Python. It has a lot of useful libraries almost across every domain. If you ever coded with java you will find Python much easier than a language such as matlab. Mohsen Ghorbian
You don't need any particular language, but Python is widely used in the science community as well as in the industry (and other fields close to data processing, such as computer vision or AI). The fact that it's Open Source is another benefit in my book.
It also allows for a smooth transition to other programming languages.
In my experience MATLAB, while widely used in academia, is a more exotic language and tool set for the industry world (and lacks the driving community factor of Python).
Python is a highly functional programming language it can do almost what other languages can do with comparable speed. It is used to make data analysis, create GUIs and websites. Python is simple enough for things to happen (really) quickly and powerful enough to allow the implementation of the most complex ideas.
Both Python and R are widely used for data processing and analysis. Python has a wide range of functions, so does R. Which program would be be appropriate for you, really depends on what types of expertises and skills you have and how comfortable you are with programming. I used both R and Python and R seems more appropriate to me since I am not too familiar with traditional programming. If you are not a programmer, R is best for you and your data (since I believe both of the programming languages have quite similar functionalities). On the contrary, if you are little comfortable with programming, you should go for Python.
"Data processing" is a very, very broad concept that encompasses everything from payroll & inventory to genomics. If you truly mean this in the broad sense, then there are literally dozens of languages that could be good candidates under various circumstances and and application areas.
If you have loaded and cleaned data and want to analyze it (I'd call that Data Analysis), I agree with most of the above - MATLAB, R, Python (with NumPy, and probably several other packages.)
If you want to extract, clean and load, there are others - Java, C#, and yes, Python. To a slightly lesser degree, R, and to a much lesser degree, Matlab.
In these days R programming is good for data analysis and advanced statistical analysis as well as PhD and Master thesis research compilation , i prefer once again R