Get Placeholders in Graph

get_placeholders.py

from tensorflow.python.framework import ops

def get_placeholders(graph):
    """Get placeholders of a graph.
    For example:
    ```python
    a = tf.placeholder(dtype=tf.float32, shape=[2, 2], name='a')
    a = tf.placeholder(dtype=tf.int32, shape=[3, 2], name='b')
    # would give [<tf.Tensor 'a:0' shape=(2, 2) dtype=float32>,
    # <tf.Tensor 'b:0' shape=(3, 2) dtype=int32>]
    tf.contrib.framework.get_placeholders(tf.get_default_graph())
    ```
    Args:
    graph: A tf.Graph.
    Returns:
    A list contains all placeholders of given graph.
    Raises:
    TypeError: If `graph` is not a tensorflow graph.
    """

    if not isinstance(graph, ops.Graph):
        raise TypeError("Input graph needs to be a Graph: %s" % graph)

    # For each placeholder() call, there is a corresponding
    # operation of type 'Placeholder' registered to the graph.
    # The return value (a Tensor) of placeholder() is the
    # first output of this operation in fact.
    operations = graph.get_operations()
    result = [i.outputs[0] for i in operations if i.type == "Placeholder"]
    return result

get_placeholders(tf.get_default_graph())