How to pass an entire list as command line argument in Python?

Question

I was trying to pass two lists containing integers as arguments to a python code. But sys.argv[i] gets the parameters as a list of string.

Input would look like,

$ python filename.py [2,3,4,5] [1,2,3,4]

I found the following hack to convert the list.

strA = sys.argv[1].replace('[', ' ').replace(']', ' ').replace(',', ' ').split()
strB = sys.argv[2].replace('[', ' ').replace(']', ' ').replace(',', ' ').split()
A = [float(i) for i in strA]
B = [float (i) for i in strB]

Is there a better way to do this?

Answer 1

Don't reinvent the wheel. Use the argparse module, be explicit and pass in actual lists of parameters

import argparse
# defined command line options
# this also generates --help and error handling
CLI=argparse.ArgumentParser()
CLI.add_argument(
  "--lista",  # name on the CLI - drop the `--` for positional/required parameters
  nargs="*",  # 0 or more values expected => creates a list
  type=int,
  default=[1, 2, 3],  # default if nothing is provided
)
CLI.add_argument(
  "--listb",
  nargs="*",
  type=float,  # any type/callable can be used here
  default=[],
)

# parse the command line
args = CLI.parse_args()
# access CLI options
print("lista: %r" % args.lista)
print("listb: %r" % args.listb)

You can then call it using

$ python my_app.py --listb 5 6 7 8 --lista  1 2 3 4
lista: [1, 2, 3, 4]
listb: [5.0, 6.0, 7.0, 8.0]