Why is Python so popular for data science?

All the major projects in deep-learning and neural networks are seeming to converge on Python as a glue language. As a long time Python engineer, I am utterly confused. I would think that there are better tools for this job.

1. Python is slow and won’t be able to implement custom logic.
2. Python is fairly hard to bind to from C++ or even C.
3. Python is stuck in a gridlocked transition from version 2.7 to 3.0

And yet, here we are programming our GPUs with Tensorflow, Theano, Keras, Lasagne etc..

What in the world could have united so many projects onto this one language? Have the religious wars ended or are data-scientists more enlightened than the rest of us? Maybe someone can point me to some rationale or manifesto, because I am totally lost on this one.

— Student