To say that Python is one of google's main languages might be a bit of an overstatement. I think that they are mainly a C++/Go/Java shop and use Python for glue code, or so I have been told by employees. This could be wrong, though.
"Glue code" might be a little unfair, but it does tend to be much more used for internal tools than customer-facing code. I don't know official numbers, but I would think it'd still be still the #3 language after C++ and Java.