ch02_7.py

import tensorflow as tf

# Define a matrix and negate it
matrix = tf.constant([[1., 2.]])
negMatrix = tf.neg(matrix)

# Start the session with a special config passed into the constructor to enable logging
with tf.Session(config=tf.ConfigProto(log_device_placement=True)) as sess:
    # Evaluate negMatrix
    result = sess.run(negMatrix)

# Print the resulting value
print(result)