NameError: name '__file__' is not defined

NameError                                 Traceback (most recent call last)<ipython-input-4-f4786694efdb> in <module>     
43     print((sess.run(accuracy, feed_dict={x:data.test.images,y_:data.test.labels})))     
44     path=saver.save(---> 
45         sess,os.path.join(os.path.dirname(__file__),'data','regression.ckpt'),     
46         write_meta_graph=False,write_state=False)     
47     print('Saved:',path)
NameError: name '__file__' is not defined