The sklearn library contains a lot of efficient tools for machine learning and statistical modeling including classification, regression, clustering and dimensionality reduction
Keras is compact, easy to learn, high-level Python library run on top of TensorFlow framework.
Since 2017, Google made Colaboratory free for public use. Colaboratory is now known as Google Colab or simply Colab.
Another attractive feature that Google offers to the developers is the use of GPU. Colab supports GPU and it is totally free. The reasons for making it free for the public could be to make its software a standard in academics for teaching machine learning and data science.
https://www.analyticsvidhya.com/blog/2015/01/scikit-learn-python-machine-learning-tool/
https://www.tensorflow.org
https://www.tutorialspoint.com/tensorflow/tensorflow_keras.htm
https://medium.com/analytics-vidhya/welcome-to-google-colab-tricks-and-tweaks-part-2-54cef0cc7d2
https://www.tutorialspoint.com/google_colab/google_colab_tutorial.pdf