Confusion-matrix clarification from Python
it's the first one  

0   [[724258    438]       
1   [ 25396    302]]      
       0         1  


According to the documentation 

sklearn.metrics.confusion_matrix(y_true, y_pred, labels=None, sample_weight=None) 



  labels : array, shape = [n_classes], optional List of labels to index
  the matrix. This may be used to reorder or select a subset of labels.
  If none is given, those that appear at least once in y_true or y_pred
  are used in sorted order.