<p>Selu is not in your <code>activations.py</code> of keras (most likely because it was added Jun 14, 2017, only <a href="https://github.com/fchollet/keras/commit/21cf50734a6996da7023dc500bdcc8ac7d74ef48#diff-2a1c58fc96ce9cf0b88487249b21a319" rel="nofollow noreferrer">22 days</a> ago). You can just add the <a href="https://github.com/fchollet/keras/blob/master/keras/activations.py" rel="nofollow noreferrer">missing code</a> in the <code>activations.py</code> file or create your own <code>selu</code> activation in the script.</p>

<p><strong>Example code</strong></p>

<pre><code>from keras.activations import elu

def selu(x):
    """Scaled Exponential Linear Unit. (Klambauer et al., 2017)
    # Arguments
        x: A tensor or variable to compute the activation function for.
    # References
        - [Self-Normalizing Neural Networks](https://arxiv.org/abs/1706.02515)
    """
    alpha = 1.6732632423543772848170429916717
    scale = 1.0507009873554804934193349852946
    return scale * elu(x, alpha)

model.add(Dense(32, input_shape=(input_length - 1,)), activation=selu)
</code></pre>

<hr>

<p>NOTE:</p>

<p>With tensorflow 2.0 keras is included. You can get the selu activation with:</p>

<pre><code>from tensorflow.keras.activations import selu
</code></pre>
Error using 'selu' activation function with Keras
<p>I'm using Keras with Tensorflow backend. When I'm trying to use the 'selu' activation function using: </p>

<pre><code>model.add(Dense(32, input_shape=(input_length - 1,)))
model.add(Activation('selu'))
</code></pre>

<p>The error I get is: </p>

<pre><code>ValueError: Unknown activation function:selu
</code></pre>

<p>Is there any solution to this?</p>