How to create a neural network without any different libraries?

Question

Neural networks

I know Python a little bit.
How to write your own neural network?
Without using all sorts of tensorflow and theano.
In pure Python.
Can you recommend literature?
Should I use multithreading when training or do I need to use a video card?
What libraries can work with a video card as a calculator?
Or do I still need to use some other languages ​​with Python?

Answer 1

Hold on, it helped me a lot. Only I rewrote everything for pluses.