TypeError: Fetch argument None has invalid type <class 'NoneType'>

When using the wrong tensorflow tf.summary visualization tools: TypeError: Fetch argument None has invalid type <class 'NoneType'>

 

Code:

初始化：
self.merged = tf.summary.merge_all()
self.writer = tf.summary.FileWriter("logs/val", sess.graph)

使用：

test = sess.run(self.merged, {self.input_state: feed_state,
                 self.input_action: feed_action,
                 self.y: feed_y})
self.writer.add_summary(test, 1)


错误原因：

self.merged = tf.summary.merge_all () on the front init variables are initialized, resulting in self.merged is NoneType