tensorflow_常见错误

'NoneType' object is not iterable

产生原因：

当sess.run的第一个参数列表和返回值列表不匹配时，会出现这个错误。比如：

with tf.Session() as sess:
    init = tf.global_variables_initializer()
    sess.run(init)

    eval, cost = sess.run(evaluation_step, feed_dict={xxx})

修改之后就可以了：

with tf.Session() as sess:
    init = tf.global_variables_initializer()
    sess.run(init)

    eval, cost = sess.run([evaluation_step, cost], feed_dict={xxx})