Custom Loss Function Keras Python | How to create a custom loss function in Keras

All you have to do is define a function for that, using keras backend functions for calculations. The function must take the true values and the model predicted values.

Now, since I’m not sure about what are g, q, x an y in your function, I’ll just create a basic example here without caring about what it means or whether it’s an actual useful function:

import keras.backend as Kdef customLoss(yTrue,yPred):    return K.sum(K.log(yTrue) - K.log(yPred))

All backend functions can be seen here: https://keras.io/backend/#backend-functions

After that, compile your model using that function instead of a regular one:

model.compile(loss=customLoss, optimizer = .....)