tensorflow_backend.py 文件源码

def placeholder(shape=None, ndim=None, dtype=_FLOATX, sparse=False, name=None):
    '''Instantiates a placeholder.

    # Arguments
        shape: shape of the placeholder
            (integer tuple, may include None entries).
        ndim: number of axes of the tensor.
            At least one of {`shape`, `ndim`} must be specified.
            If both are specified, `shape` is used.
        dtype: placeholder type.
        name: optional name string for the placeholder.

    # Returns
        Placeholder tensor instance.
    '''
    if not shape:
        if ndim:
            shape = tuple([None for _ in range(ndim)])
    if sparse:
        x = tf.sparse_placeholder(dtype, name=name)
        x._dims = len(shape)
    else:
        x = tf.placeholder(dtype, shape=shape, name=name)
    x._keras_shape = shape
    x._uses_learning_phase = False
    return x