tf.placeholder(dtype, shape=None, name=None)###
Inserts a placeholder for a tensor that will be always fed.
插入一个待初始化的张量占位符
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().
For example:
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.
重要事项：这个张量被求值时会产生错误。 它的值必须在Session.run(), Tensor.eval() 或 Operation.run() 中使用feed_dict的这个可选参数来填充。
例外：
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).
参数：
dtype：被填充的张量的元素类型。
shape：被填充张量的形状(可选参数)。如果没有指定张量打形状，你可以填充该张量为任意形状。
name：为该操作提供一个名字(可选参数)。
Returns:
A Tensor. that may be used as a handle for feeding a value, but not evaluated directly.
返回值：
一个张量. 必须在使用句柄的情况下赋值，但不可以直接求值。
