I mostly use Python for web development and I've stopped using Python 2 for that with 3.5, so in early 2016, but I do remember that some machine learning or dat

I mostly use Python for web development and I've stopped using Python 2 for that with 3.5, so in early 2016, but I do remember that some machine learning or data analysis tools were stuck on Py2 for a little longer. I definitely wouldn't say that half of popular libraries in general didn't support python 3 at all back then, but for some use cases that may have been true tho.