title: Training only one output of a network in Keras
body: <p>I have a network in Keras with many outputs, however, my training data only provides information for a single output at a time.</p>
  
  <p>At the moment my method for training has been to run a prediction on the input in question, change the value of the particular output that I am training and then doing a single batch update. If I'm right this is the same as setting the loss for all outputs to zero except the one that I'm trying to train.</p>
  
  <p>Is there a better way? I've tried class weights where I set a zero weight for all but the output I'm training but it doesn't give me the results I expect?</p>
  
  <p>I'm using the Theano backend.</p>