As learned earlier, Keras model represents the actual neural network model. Keras provides a two mode to create the model, simple and easy to use Sequential API as well as more flexible and advanced Functional API. Let us learn now to create model using both Sequential and Functional API in this blog.

Sequential

The core idea of Sequential API is simply arranging the Keras layers in a sequential order and so, it is called Sequential API. Most of the ANN also has layers in sequential order and the data flows from one layer to another layer in the given order until the data finally reaches the output layer.

A ANN model can be created by simply calling Sequential() API as specified below −

from keras.models import Sequential
model = Sequential()

Add layers

To add a layer, simply create a layer using Keras layer API and then pass the layer through add() function as specified below −

from keras.models import Sequential
model = Sequential()
input_layer = Dense(32, input_shape=(8,)) model.add(input_layer)
hidden_layer = Dense(64, activation='relu'); model.add(hidden_layer)
output_layer = Dense(8)
model.add(output_layer)

Here, we have created one input layer, one hidden layer and one output layer.

Access the model

Keras provides few methods to get the model information like layers, input data and output data. They are as follows −

model.layers − Returns all the layers of the model as list.

>>> layers = model.layers
>>> layers
[
<keras.layers.core.Dense object at 0x000002C8C888B8D0>,
<keras.layers.core.Dense object at 0x000002C8C888B7B8>
<keras.layers.core.Dense object at 0x 000002C8C888B898>
]
model.inputs − Returns all the input tensors of the model as list.
>>> inputs = model.inputs
>>> inputs
[<tf.Tensor 'dense_13_input:0' shape=(?, 8) dtype=float32>]
model.outputs − Returns all the output tensors of the model as list.
>>> outputs = model.outputs
>>> outputs
<tf.Tensor 'dense_15/BiasAdd:0' shape=(?, 8) dtype=float32>]
model.get_weights − Returns all the weights as NumPy arrays.
model.set_weights(weight_numpy_array) − Set the weights of the model.

Serialize the model

Keras provides methods to serialize the model into object as well as json and load it again later. They are as follows −

get_config() − IReturns the model as an object.

config = model.get_config()

from_config() − It accept the model configuration object as argument and create the model accordingly.

new_model = Sequential.from_config(config)

to_json() − Returns the model as an json object.

>>> json_string = model.to_json()
>>> json_string '{"class_name": "Sequential", "config":
{"name": "sequential_10", "layers":
[{"class_name": "Dense", "config":
{"name": "dense_13", "trainable": true, "batch_input_shape":
[null, 8], "dtype": "float32", "units": 32, "activation": "linear",
"use_bias": true, "kernel_initializer":
{"class_name": "Vari anceScaling", "config":
{"scale": 1.0, "mode": "fan_avg", "distribution": "uniform", "seed": null}},
"bias_initializer": {"class_name": "Zeros", "conf
ig": {}}, "kernel_regularizer": null, "bias_regularizer": null,
"activity_regularizer": null, "kernel_constraint": null, "bias_constraint": null}},
{" class_name": "Dense", "config": {"name": "dense_14", "trainable": true,
"dtype": "float32", "units": 64, "activation": "relu", "use_bias": true,
"kern el_initializer": {"class_name": "VarianceScaling", "config":
{"scale": 1.0, "mode": "fan_avg", "distribution": "uniform", "seed": null}},
"bias_initia lizer": {"class_name": "Zeros",
"config": {}}, "kernel_regularizer": null, "bias_regularizer": null,
"activity_regularizer": null, "kernel_constraint" : null, "bias_constraint": null}},
{"class_name": "Dense", "config": {"name": "dense_15", "trainable": true,
"dtype": "float32", "units": 8, "activation": "linear", "use_bias": true,
"kernel_initializer": {"class_name": "VarianceScaling", "config":
{"scale": 1.0, "mode": "fan_avg", "distribution": " uniform", "seed": null}},
"bias_initializer": {"class_name": "Zeros", "config": {}},
"kernel_regularizer": null, "bias_regularizer": null, "activity_r egularizer":
null, "kernel_constraint": null, "bias_constraint":
null}}]}, "keras_version": "2.2.5", "backend": "tensorflow"}'
>>>
model_from_json() − Accepts json representation of the model and create a new model.
from keras.models import model_from_json
new_model = model_from_json(json_string)
to_yaml() − Returns the model as a yaml string.
>>> yaml_string = model.to_yaml()
>>> yaml_string 'backend: tensorflow\nclass_name:
Sequential\nconfig:\n layers:\n - class_name: Dense\n config:\n
activation: linear\n activity_regular izer: null\n batch_input_shape:
!!python/tuple\n - null\n - 8\n bias_constraint: null\n bias_initializer:\n
class_name : Zeros\n config: {}\n bias_regularizer: null\n dtype:
float32\n kernel_constraint: null\n
kernel_initializer:\n cla ss_name: VarianceScaling\n config:\n
distribution: uniform\n mode: fan_avg\n
scale: 1.0\n seed: null\n kernel_regularizer: null\n name: dense_13\n
trainable: true\n units: 32\n
use_bias: true\n - class_name: Dense\n config:\n activation: relu\n activity_regularizer: null\n
bias_constraint: null\n bias_initializer:\n class_name: Zeros\n
config : {}\n bias_regularizer: null\n dtype: float32\n
kernel_constraint: null\n kernel_initializer:\n class_name: VarianceScalin g\n
config:\n distribution: uniform\n mode: fan_avg\n scale: 1.0\n
seed: null\n kernel_regularizer: nu ll\n name: dense_14\n trainable: true\n
units: 64\n use_bias: true\n - class_name: Dense\n config:\n
activation: linear\n activity_regularizer: null\n
bias_constraint: null\n bias_initializer:\n
class_name: Zeros\n config: {}\n bias_regu larizer: null\n
dtype: float32\n kernel_constraint: null\n
kernel_initializer:\n class_name: VarianceScaling\n config:\n
distribution: uniform\n mode: fan_avg\n
scale: 1.0\n seed: null\n kernel_regularizer: null\n name: dense _15\n
trainable: true\n units: 8\n
use_bias: true\n name: sequential_10\nkeras_version: 2.2.5\n'
>>>
model_from_yaml() − Accepts yaml representation of the model and create a new model.
from keras.models import model_from_yaml
new_model = model_from_yaml(yaml_string)
Summarise the model
Understanding the model is very important phase to properly use it for training and prediction purposes. Keras provides a simple method, summary to get the full information about the model and its layers.
A summary of the model created in the previous section is as follows −
>>> model.summary() Model: "sequential_10"
_________________________________________________________________
Layer (type) Output Shape Param
#================================================================
dense_13 (Dense) (None, 32) 288
_________________________________________________________________
dense_14 (Dense) (None, 64) 2112
_________________________________________________________________
dense_15 (Dense) (None, 8) 520
=================================================================
Total params: 2,920
Trainable params: 2,920
Non-trainable params: 0
_________________________________________________________________
>>>

Train and Predict the model

Model provides function for training, evaluation and prediction process. They are as follows −

compile − Configure the learning process of the model
fit − Train the model using the training data
evaluate − Evaluate the model using the test data
predict − Predict the results for new input.

Functional API

Sequential API is used to create models’ layer-by-layer. Functional API is an alternative approach of creating more complex models. Functional model, you can define multiple input or output that share layers. First, we create an instance for model and connecting to the layers to access input and output to the model. This section explains about functional model in brief.

Create a model

Import an input layer using the below module −
>>> from keras.layers import Input
Now, create an input layer specifying input dimension shape for the model using the below code −
>>> data = Input(shape=(2,3))
Define layer for the input using the below module −
>>> from keras.layers import Dense
Add Dense layer for the input using the below line of code −
>>> layer = Dense(2)(data)
>>> print(layer)
Tensor("dense_1/add:0", shape =(?, 2, 2), dtype = float32)
Define model using the below module −
from keras.models import Model
Create a model in functional way by specifying both input and output layer −
model = Model(inputs = data, outputs = layer)
The complete code to create a simple model is shown below −
from keras.layers import Input
from keras.models import Model
from keras.layers import Dense
data = Input(shape=(2,3))
layer = Dense(2)(data) model =
Model(inputs=data,outputs=layer) model.summary()
_________________________________________________________________
Layer (type)               Output Shape               Param #
=================================================================
input_2 (InputLayer)       (None, 2, 3)               0
_________________________________________________________________
dense_2 (Dense)            (None, 2, 2)               8
=================================================================
Total params: 8
Trainable params: 8
Non-trainable params: 0
_________________________________________________________________

So, this brings us to the end of blog. This Tecklearn ‘Create Model using both Sequential and Functional API in Keras’ blog helps you with commonly asked questions if you are looking out for a job in Artificial Intelligence. If you wish to learn Artificial Intelligence and build a career in AI or Machine Learning domain, then check out our interactive, Artificial Intelligence and Deep Learning with TensorFlow Training, that comes with 24*7 support to guide you throughout your learning period. Please find the link for course details:

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Pre-requisites for AI & DL
Python Programming Language
Installation & IDE

Environment Set Up and Essentials

Installation
Python – NumPy
Python for Data Science and AI
Python Language Essentials
Python Libraries – Numpy and Pandas
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More Prerequisites for Deep Learning and AI

Pandas for Data Analysis
Machine Learning Basic Concepts
Normalization
Data Set
Machine Learning Concepts
Regression
Logistic Regression
SVM – Support Vector Machines
Decision Trees
Python Libraries for Data Science and AI

Introduction to Neural Networks

Creating Module
Neural Network Equation
Sigmoid Function
Multi-layered perception
Weights, Biases
Activation Functions
Gradient Decent or Error function
Epoch, Forward & backword propagation
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TensorFlow code-basics
Graph Visualization
Constants, Placeholders, Variables

Multi-layered Neural Networks

Error Back propagation issues
Drop outs

Regularization techniques in Deep Learning

Deep Learning Libraries

Tensorflow
Keras
OpenCV
SkImage
PIL

Building of Simple Neural Network from Scratch from Simple Equation

Training the model

Dual Equation Neural Network

TensorFlow
Predicting Algorithm

Introduction to Keras API

Define Keras
How to compose Models in Keras
Sequential Composition
Functional Composition
Predefined Neural Network Layers
What is Batch Normalization
Saving and loading a model with Keras
Customizing the Training Process
Using TensorBoard with Keras
Use-Case Implementation with Keras

GPU in Deep Learning

Introduction to GPUs and how they differ from CPUs
Importance of GPUs in training Deep Learning Networks
The GPU constituent with simpler core and concurrent hardware
Keras Model Saving and Reusing
Deploying Keras with TensorBoard

Keras Cat Vs Dog Modelling

Activation Functions in Neural Network

Optimization Techniques

Some Examples for Neural Network

Convolutional Neural Networks (CNN)

Introduction to CNNs
CNNs Application
Architecture of a CNN
Convolution and Pooling layers in a CNN
Understanding and Visualizing a CNN

RNN: Recurrent Neural Networks

Introduction to RNN Model
Application use cases of RNN
Modelling sequences
Training RNNs with Backpropagation
Long Short-Term memory (LSTM)
Recursive Neural Tensor Network Theory
Recurrent Neural Network Model

Application of Deep Learning in image recognition, NLP and more

Real world projects in recommender systems and others

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