# AI News, How to build your own Neural Network from scratch in Python ## How to build your own Neural Network from scratch in Python

Motivation: As part of my personal journey to gain a better understanding of Deep Learning, I’ve decided to build a Neural Network from scratch without a deep learning library like TensorFlow.

Without delving into brain analogies, I find it easier to simply describe Neural Networks as a mathematical function that maps a given input to a desired output.

Neural Networks consist of the following components The diagram below shows the architecture of a 2-layer Neural Network (note that the input layer is typically excluded when counting the number of layers in a Neural Network) Creating a Neural Network class in Python is easy.

Training the Neural Network The output ŷ of a simple 2-layer Neural Network is: You might notice that in the equation above, the weights W and the biases b are the only variables that affects the output ŷ.

As we’ve seen in the sequential graph above, feedforward is just simple calculus and for a basic 2-layer neural network, the output of the Neural Network is: Let’s add a feedforward function in our python code to do exactly that.

In order to know the appropriate amount to adjust the weights and biases by, we need to know the derivative of the loss function with respect to the weights and biases.

However, we can’t directly calculate the derivative of the loss function with respect to the weights and biases because the equation of the loss function does not contain the weights and biases.

Although Deep Learning libraries such as TensorFlow and Keras makes it easy to build deep nets without fully understanding the inner workings of a Neural Network, I find that it’s beneficial for aspiring data scientist to gain a deeper understanding of Neural Networks.

Normalized Inputs and Initial Weights

This video is part of the Udacity course "Deep Learning". Watch the full course at

But what *is* a Neural Network? | Chapter 1, deep learning

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This video is part of the Udacity course "Deep Learning". Watch the full course at