Useful Python Modules argparse()

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Parent Category: Coding
Category: Python

argparse

The argparse module makes it easy to write user-friendly command-line interfaces. The program defines what arguments it requires, and argparse will figure out how to parse those out of sys.argv. The argparse module also automatically generates help and usage messages. The module will also issue errors when users give the program invalid arguments.reference here link

argparse.ArgumentParser()
parser = argparse.ArgumentParser(
                    prog='ProgramName',
                    description='What the program does',
                    epilog='Text at the bottom of help')
Example

 

 
ArgumentParser.add_argument

method attaches individual argument specifications to the parser. It supports positional arguments, options that accept values, and on/off flags:

 

Quick Links for add_argument()

Name

Description

Values

action

Specify how an argument should be handled

'store', 'store_const', 'store_true', 'append', 'append_const', 'count', 'help', 'version'

choices

Limit values to a specific set of choices

['foo', 'bar'], range(1, 10), or Container instance

const

Store a constant value

  

default

Default value used when an argument is not provided

Defaults to None

dest

Specify the attribute name used in the result namespace

  

help

Help message for an argument

  

metavar

Alternate display name for the argument as shown in help

  

nargs

Number of times the argument can be used

int, '?', '*', or '+'

required

Indicate whether an argument is required or optional

True or False

type

Automatically convert an argument to the given type

int, float, argparse.FileType('w'), or callable function
 
Example 1
import argparse

parser = argparse.ArgumentParser(description='Here are the Camera Settings')
parser.add_argument('--imgdir', help = 'Folder to store images in',default='Pics')
parser.add_argument('--resolution',help = 'Desired resloution',default='1280x720')
                   
args = parser.parse_args()
print(args.imgdir)
print(args.resolution)
 
Example 2
import argparse

parser = argparse.ArgumentParser(description='Process some integers.')
parser.add_argument('integers', metavar='N', type=int, nargs='+',
                    help='an integer for the accumulator')
parser.add_argument('--sum', dest='accumulate', action='store_const',
                    const=sum, default=max,
                    help='sum the integers (default: find the max)')

args = parser.parse_args()
print(args.accumulate(args.integers))

Assuming the above Python code is saved into a file called prog.py, it can be run at the command line and it provides useful help messages:

$ python prog.py -h
usage: prog.py [-h] [--sum] N [N ...]

Process some integers.

positional arguments:
 N           an integer for the accumulator

options:
 -h, --help  show this help message and exit
 --sum       sum the integers (default: find the max)

When run with the appropriate arguments, it prints either the sum or the max of the command-line integers:

$ python prog.py 1 2 3 4
4

$ python prog.py 1 2 3 4 --sum
10

If invalid arguments are passed in, an error will be displayed:

$ python prog.py a b c
usage: prog.py [-h] [--sum] N [N ...]
prog.py: error: argument N: invalid int value: 'a'