Pandas Dataframe structure makes it very simple to arrange and adjust data. When used with SciPy it makes Machine Learning an easy process.

The library is very intuitive. Most operation follow verb_noun pattern and even if you are a new user, you can "guess" what possibly the operation will be. It makes working with series and data frames very easy and most of times, you will find a highly optimized function in the library for whatever operation you want to perform.

Easy to use with large datasets in Python, easy to setup with Anaconda