It doesn't really support things like survival analysis, complicated time series models or (the most important) missing data.
Also, R's formula interface for models is a thing of beauty, while Python has nothing similar.
So, if you have data with no missings and are only interested in a small subset of statistics (that used by computer scientists), then Python can definitely suffice.
If you are in almost any other discipline, you're going to be using R.
Don't get me wrong, Python is a wonderful language, but R is so well adapted to analysis that it will be a very long time before it gets replaced (Julia looks really promising, but its not at 1.0 yet, and hence hasn't seen the broad scale adoption it would need).