Simple Session

import tensorflow as tf

import os
os.environ['TF_CPP_MIN_LOG_LEVEL'] = '2'
hello = tf.constant('Hello, TensorFlow!')
hello
<tf.Tensor 'Const:0' shape=() dtype=string>

sess = tf.Session()
sess.run(hello)
b'Hello, TensorFlow!'

a = tf.constant(20)
b = tf.constant(30)
sess.run(a + b)
50

sess.close()