The argparse module provides a convenient interface to handle the command line arguments. It displays the generic usage of the program, help, and errors.
usage is a parameter of the ArgumentParses object. Its purpose is to display a string with information about the program and its arguments. By default, usage uses the program’s arguments to construct a usage message.
The following example demonstrates how to run a program with command-line arguments using the argparse module.
The program program.py takes a single command-line argument for the radius and calculates the area of the circle. The ArgumentParser object parser is created to add arguments and parse them.
import mathimport argparse#create an ArgumentParser objectparser = argparse.ArgumentParser(description = 'Calculate radius of the circle')#declare argumentsparser.add_argument('-r','--radius', type = int, required = True, help='radius of the circle')args = parser.parse_args()def area_circle(radius):return (math.pi*radius*radius)def main():area = area_circle(args.radius)print(area)main()
Entering --help displays information about the program, including its arguments and usage. By default, usage is a message calculated from the argument names, as illustrated below.
>> python program.py --help
usage: program.py [-h] -r RADIUS
Calculate radius of the circle
optional arguments:
-h, --help show this help message and exit
-r RADIUS, --radius RADIUS
radius of the circle
usage can be overridden by specifying the usage keyword argument, as shown in line 4 of the below program.
import mathimport argparseparser = argparse.ArgumentParser(description = 'Calculate radius of the circle', prog = 'My program', usage = '%(prog)s [options]')parser.add_argument('-r','--radius', type = int, required = True, help='radius of the circle')args = parser.parse_args()def area_circle(radius):return (math.pi*radius*radius)def main():area = area_circle(args.radius)print(area)main()
Now, the user-specified message is displayed as the usage of the program, as illustrated below.
>>python program.py --help
usage: My program [options]
Calculate radius of the circle
optional arguments:
-h, --help show this help message and exit
-r RADIUS, --radius RADIUS
radius of the circle
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