Selenium is an open-source tool. Selenium is used in software testing for web-application. Both Python and Java have some over other language.Both are simple and easy to learn languages. Between these I will recommend Python for software testing framework. There are many reasons for that which I am mentioning below:
Python is a scripted language which makes it easy to integrate and communicate with other language like HTML ,C++ and Java.
As compared to Java, Python is very easy to learn.
There are dozens of supporting tools available for Python (for testing API and BDD are popular )
If you want to make your career in automation testing using Python you must have a look at the following Selenium Training Course. You should also watch the video tutorial.
Here is the video tutorial on Python: