Several ways to pass parameters when running python script

If you need to pass some parameters when you run the python script, for example, gpusand batch_sizecan be used in three ways.

python script.py 0,1,2 10
python script.py -gpus=0,1,2 --batch-size=10
python script.py -gpus=0,1,2 --batch_size=10

These three different analytical methods format parameters correspond, respectively sys.argv,argparse、 tf.app.run， two are python carrying function, which is tensorflowa convenient way to provide.

1.sys.argv

sys Module is very common module, which encapsulates the data associated with the python interpreter, for example, sys.modules which has all of the loaded module information, sys.path which is PYTHONPATH content, and sys.argv then encapsulates the incoming data parameters.
Use sys.argv parametrically receiving the first command above comprising the following:

import sys
gpus = sys.argv[1]
#gpus = [int(gpus.split(','))]
batch_size = sys.argv[2]
print(gpus)
print(batch_size)

2.argparse

import argparse
parser = argparse.ArgumentParser(description='manual to this script')
parser.add_argument("--gpus", type=str, default="0")
parser.add_argument("--batch-size", type=int, default=32)
args = parser.parse_args()
print(args.gpus)
print(args.batch_size)

Note that, the script runs the command python script.py -gpus=0,1,2 --batch-size=10 in --batch-size will be automatically parsed into batch_size .
parser.add_argument Method type parameter can theoretically be any type of legitimate, but some argument to format is too much trouble, such as list, so the general use bool , int , str , float these basic types on the line the more complex needs can be str passed, and then manually resolve. bool Special type of parsing, any incoming value will be parsed into True , if passed as null False

3.tf.app.run

import tensorflow as tf
tf.app.flags.DEFINE_string('gpus', None, 'gpus to use')
tf.app.flags.DEFINE_integer('batch_size', 5, 'batch size')

FLAGS = tf.app.flags.FLAGS

def main(_):
    print(FLAGS.gpus)
    print(FLAGS.batch_size)

if __name__=="__main__":
    tf.app.run()

There are several points to note:

tensorflowProvide only the following methods:

tf.app.flags.DEFINE_string, , , Four methods, respectively , , , types of arguments. Here to resolve more stringent, incoming 1 will be parsed into , any remaining value will be parsed into .
tf.app.flags.DEFINE_integer
tf.app.flags.DEFINE_boolean
tf.app.flags.DEFINE_floatstrintboolfloatboolTrueFalse

To receive a script you need to define a parameter of mainthe method: def main(_):This parameter is passed in the name of the script, generally with less than, the receiver underlined.

With batch_sizeparameters for example, the name used when this parameter is passed --batch_size, that is to say, not as underlined in argparsethe same was resolved to underline.

tf.app.run()Entrance will find and execute the script mainmethod. Only in the execution tf.app.run()order from then FLAGSremoved parameters.
From its signature look, it also can specify your own methods need to be performed, not necessarily have to be called main:

Several ways to pass parameters when running python script

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