import tensorflow as tf

A = tf.placeholder(tf.float32, shape=(None, 3))
B = A + 5

with tf.Session() as sess:
    B_val_1 = B.eval(feed_dict={A: [[1,2,3]]})
    B_val_2 = B.eval(feed_dict={A: [[4,5,6], [7,8,9]]})

print B_val_1
print B_val_2