Tensorflow代码不生成事件文件

Question

有人知道为什么此代码在当前目录中不生成事件文件吗？

from __future__ import absolute_import
from __future__ import division
from __future__ import print_function

import numpy as np
import tensorflow as tf
import sys
print(sys.version)

a = tf.constant(3.0, dtype=tf.float32)
b = tf.constant(4.0) # also tf.float32 implicitly
total = a + b
print(a)
print(b)
print(total)

writer = tf.summary.FileWriter('.')
writer.add_graph(tf.get_default_graph())