在一些github上公开的代码中，我们经常会看到这样的程序if __name__ == '__main__':

tf.app.run()

像网上的大多数文章一样，先粘贴一下run()的源码：def run(main=None, argv=None):

"""Runs the program with an optional 'main' function and 'argv' list."""

f = flags.FLAGS

# Extract the args from the optional `argv` list.

args = argv[1:] if argv else None

# Parse the known flags from that list, or from the command

# line otherwise.

# pylint: disable=protected-access

flags_passthrough = f._parse_flags(args=args)

# pylint: enable=protected-access

main = main or _sys.modules['__main__'].main

# Call the main function, passing through any arguments

# to the final program.

_sys.exit(main(_sys.argv[:1] + flags_passthrough))

_allowed_symbols = [

'run',

# Allowed submodule.

'flags',

]

remove_undocumented(__name__, _allowed_symbols)

源码中写的很清楚，首先加载flags的参数项，然后执行main()函数，其中参数使用tf.app.flags.FLAGS定义的。

tf.app.flags.FLAGS# fila_name: temp.py

import tensorflow as tf

FLAGS = tf.app.flags.FLAGS

tf.app.flags.DEFINE_string('string', 'train', 'This is a string')

tf.app.flags.DEFINE_float('learning_rate', 0.001, 'This is the rate in training')

tf.app.flags.DEFINE_boolean('flag', True, 'This is a flag')

print('string: ', FLAGS.string)

print('learning_rate: ', FLAGS.learning_rate)

print('flag: ', FLAGS.flag)

输出：string: train

learning_rate: 0.001

flag: True

如果在命令行中执行python3 temp.py --help，得到输出：usage: temp.py [-h] [--string STRING] [--learning_rate LEARNING_RATE]

[--flag [FLAG]] [--noflag]

optional arguments:

-h, --help show this help message and exit

--string STRING This is a string

--learning_rate LEARNING_RATE

This is the rate in training

--flag [FLAG] This is a flag

--noflag

如果要对FLAGS的默认值进行修改，只要输入命令：python3 temp.py --string 'test' --learning_rate 0.2 --flag False

联合使用import tensorflow as tf

FLAGS = tf.app.flags.FLAGS

tf.app.flags.DEFINE_string('string', 'train', 'This is a string')

tf.app.flags.DEFINE_float('learning_rate', 0.001, 'This is the rate in training')

tf.app.flags.DEFINE_boolean('flag', True, 'This is a flag')

def main(unuse_args):

print('string: ', FLAGS.string)

print('learning_rate: ', FLAGS.learning_rate)

print('flag: ', FLAGS.flag)

if __name__ == '__main__':

tf.app.run()

主函数中的tf.app.run()会调用main，并传递参数，因此必须在main函数中设置一个参数位置。如果要更换main名字，只需要在tf.app.run()中传入一个指定的函数名即可。def test(args):

# test

...

if __name__ == '__main__':

tf.app.run(test)