TensorFlow版本號:1.1.0python
placeholder的中文意思是佔位符,相似於函數參數,運行時必須傳入值。dom
def placeholder(dtype, shape=None, name=None): """Inserts a placeholder for a tensor that will be always fed. **Important**: This tensor will produce an error if evaluated. Its value must be fed using the `feed_dict` optional argument to `Session.run()`, `Tensor.eval()`, or `Operation.run()`. Args: dtype: The type of elements in the tensor to be fed. shape: The shape of the tensor to be fed (optional). If the shape is not specified, you can feed a tensor of any shape. name: A name for the operation (optional). Returns: A `Tensor` that may be used as a handle for feeding a value, but not evaluated directly. """
上述爲官方文檔中的說明,講述的很詳細。函數
dtype是指數據類型,shape是指tensor的維度,若是不指定,那麼能夠傳入任意的lua
For example: ```python x = tf.placeholder(tf.float32, shape=(1024, 1024)) y = tf.matmul(x, x) with tf.Session() as sess: print(sess.run(y)) # ERROR: will fail because x was not fed. rand_array = np.random.rand(1024, 1024) print(sess.run(y, feed_dict={x: rand_array})) # Will succeed. ```