A python is not just a rather dangerous looking animal. It also gave the name to a very powerful and popular programming language — Python. Having heard different people pronounce Python in different ways, I decided to look up its pronunciation. This is what I found.
In British English, Python is pronounced as [ˈpaɪθən], whereas in American English it is pronounced as [ˈpaɪθɑːn]. Clearly, the o is pronounced very differently, and explains what I had been hearing. You can listen to both variants here.
If English is not your native language, make sure you pronounce the th correctly (at least when speaking English), as explained previously.