Think about how many enterprise-level software apps have been developed in Java and will need to be maintained for years to come. Think about how much of such software is being developed now as you write this.

While I like Python for its seeming simplicity it lacks some nice architectural paradigms that Java has employed for years - think Inversion of control, or data access frameworks hibernate or ibatis.

Python is in a somewhat of an infancy stage to support that type of enterprise-level architectural paradigms.

For OP, if you want to get into machine learning domain then Python is definitely the language of choice.