Argparse optional positional arguments?

In Python, the argparse module can be used to specify optional positional arguments by setting the nargs parameter to '?'. Here's an example code snippet:

import argparse

parser = argparse.ArgumentParser()
parser.add_argument("input_file", nargs='?', default="default.txt")
parser.add_argument("output_file", nargs='?', default="output.txt")
args = parser.parse_args()

print(args.input_file)
print(args.output_file)

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When you run this script, the input_file and output_file arguments are optional and will default to "default.txt" and "output.txt", respectively, if they are not provided.

# When you run the script with no arguments
$ python script.py
default.txt
output.txt

# When you run the script with only one argument
$ python script.py input.txt
input.txt
output.txt

# When you run the script with two arguments
$ python script.py input.txt output.txt
input.txt
output.txt