Is it possible to program an Arduino in other languages?
It's definitely possible to use alternate languages for development with Arduino, just not necessarily using the standard IDE. This is as, at the end of the day, the C/C++ code is assembled into byte-code for the AT-chip on the Arduino board. One language you could use is Céu, a higher-level version of C/C++. The main issue that you'll have is finding a compiler for your language of choice - at the end of the day, you could write your own - however, this requires an intimate jnowledge of C/C++ anyways. Therefore, it is probably best to stick to C/C++, at least for the time being.

EDIT: You've slightly rephrased your question, so yes, it would be possible to program your Arduino in Python (poor choice of language, though that's just my opinion), but you would need a different IDE / a custom compiler for the reasons above. Also, you would have to be careful when linking libraries written in a different language for the Arduino (as they're all C/C++).