Hi,
To start with Hadoop I would suggest you learn Java first as the whole Hadoop framework is written in Java. Python is easy to learn and has a simple syntax, but as far as Hadoop is concerned, there are tools like Pig and Hive which automatically converts MapReduce programs in Java. It is not bounded but it will increase your demand when you enter the industry.
Java will be extremely important if you want to choose fields like architecture, tester, developer, administrator, etc.