def print_step(self, message, target):
    print(('%s %10.4f' % (message, target)), '[', ' '.join([('%10.4f' % a) for a in self.x]), ']')
def print_step(self, message, target):
    print(('%s %10.4f' % (message, target)), '[', ' '.join([('%10.4f' % a) for a in self.x]), ']')