how to extract a radio signal features with python?
Some of the more cutting edge signal classification techniques utilize deep neural networks (DNNs):

https://arxiv.org/pdf/1712.04578.pdf

This particular paper utilizes a convolutional neural network (CNN) and a residual neural network.  The convolutional "front-end" extracts its own nonlinear features prior to connection to the densely connected layers.

DNNs are typically very computationally expensive, so your approach to feature extraction approach might meet your requirements.