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What is argparse prefix_chars in Python?

Ayesha Naeem

The argparse module provides a convenient interface to handle command-line arguments. It displays the generic usage of the program, help, and errors.

Explanation

The parse_args() function of the ArgumentParser class parses arguments and the add_argument() function adds arguments to be accepted from the user.

Most arguments are specified through the prefix -. For instance, the value of an argument foo may be specified as --foo or -f, depending on how the user has defined the argument in the add_argument() function. The user can supply a set of prefixes to the prefix_chars argument of the ArgumentParser object to support additional prefixes.

Example

The following program demonstrates how to use the different prefixes when handling arguments.

The program sets the prefix_chars value to -+/, which means the +, /, and - characters can be used as prefixes.

The program then creates arguments with each of the three prefixes and parses the provided values for the arguments.

The default value of prefix_chars is -. If the specified value of prefix_chars does not contain -, then using - as a prefix will raise an error.

import math
import argparse

# create an ArgumentParser object
parser = argparse.ArgumentParser(description = 'Calculate radius of the circle', prefix_chars = '-+/')
# add arguments
parser.add_argument('-r','--radius', type = int)
parser.add_argument('+x', type = int)
parser.add_argument('/y', type = int)
args = parser.parse_args('-r 10 +x 6 /y 3'.split())
print(args)

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