Machine learning -- neural network

The first 1 Turn off ： Basic concepts of neural networks

The first 1 topic

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Altogether 3x4+4x2=20 A weight

The first 2 Turn off ： Activation function

Our mission ： use Python Implement common activation functions .

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def relu(x):
    '''
    x: Real numbers from negative infinity to positive infinity 
    '''
    #******