predict_in_callback.py

class MyCallBack(Callback):
    def __init__(self, x_v, y_v):
        super(MyCallBack, self).__init__()
        self.x_v, self.y_v = x_v, y_v
        self.ps = []
    
    def on_epoch_end(self, epoch, logs={}):
        p = self.model.predict(self.x_v).flatten()
        self.ps.append(p)
        logs['val_loss'] = log_loss(self.x_y, p)
        logs['val_acc'] = accuracy_score(self.x_y, p.round())
        
mycallback = MyCallBack(x_v, y_v)        
model.fit(x_t, y_t,..., callbacks=[mycallback])

print(mycallback.ps)