Tensorflow conditional statement

tf.cond.py

import tensorflow as tf

training = tf.placeholder(dtype=tf.bool, name='is_training')

a = tf.placeholder(dtype=tf.float32, name='a')
b = tf.placeholder(dtype=tf.float32, name='b')
c = tf.cond(training, lambda : a+b, lambda : a*b)

sess = tf.Session()

op = sess.run(c, feed_dict = {
    a : 1., b : 2., training : False
})

print(op) # 2.0