However you'd pronounce it when you're talking about the snake. The logo is a snake and it's spelled like the snake. I was unaware it was even debatable.
I prefer Pyth-on, but usually revert to Pythen, because here in Germany I've virtually never heard any other pronunciation.
But Python is not bugging me, what's worse is everybody mispronouncing Excel. I've never heard a single person in a business context (spreadsheet) pronounce it correctly.
For this reason I called one of my Python project "dependenpy" because _for me_ it sounds like dependency, but now I worry people read it like dependen-pie or get confused about the pronunciation.
If I speak with someone in English, I'll say pie-thon.