Optparse module in Python

Last Updated : 30 Nov, 2022

Optparse module makes easy to write command-line tools. It allows argument parsing in the python program.

optparse make it easy to handle the command-line argument.
It comes default with python.
It allows dynamic data input to change the output

Code: Creating an OptionParser object.

Python3

import optparse
parser = optparse.OptionParser()

Defining options:

It should be added one at a time using the add_option(). Each Option instance represents a set of synonymous command-line option string.

Way to create an Option instance are:

OptionParser.add_option(option)

OptionParser.add_option(*opt_str, attr=value, ...)

To define an option with only a short option string:

 parser.add_option("-f", attr=value, ....)

And to define an option with only a long option string:

parser.add_option("--foo", attr=value, ....)

Standard Option Actions:

"store": store this option’s argument (default).
"store_const": store a constant value.
"store_true": store True.
"store_false": store False.
"append": append this option’s argument to a list.
"append_const": append a constant value to a list.

Standard Option Attributes:

Option.action: (default: "store")
Option.type: (default: "string")
Option.dest: (default: derived from option strings)
Option.default: The value to use for this option’s destination if the option is not seen on the command line.

Here’s an example of using optparse module in a simple script:

Python3

# import OptionParser class 
# from optparse module.
from optparse import OptionParser

# create a OptionParser
# class object
parser = OptionParser()

# add options
parser.add_option("-f", "--file",
                  dest = "filename",
                  help = "write report to FILE", 
                  metavar = "FILE")
parser.add_option("-q", "--quiet",
                  action = "store_false", 
                  dest = "verbose", default = True,
                  help = "don't print status messages to stdout")

(options, args) = parser.parse_args()

With these few lines of code, users of your script can now do the “usual thing” on the command-line, for example:

<yourscript> --file=outfile -q

Lets, understand with an example:

Code: Writing python script for print table of n.

Python3

# import optparse module
import optparse

# define a function for 
# table of n
def table(n, dest_cheak):
    for i in range(1,11):
        tab = i*n
        
        if dest_cheak:
            print(tab)
            
    return tab

# define a function for 
# adding options
def Main():
    # create OptionParser object
    parser = optparse.OptionParser()
    
    # add options
    parser.add_option('-n', dest = 'num',
                      type = 'int', 
                      help = 'specify the n''th table number to output')
    parser.add_option('-o', dest = 'out',
                      type = 'string', 
                      help = 'specify an output file (Optional)')
    parser.add_option("-a", "--all", 
                      action = "store_true",
                      dest = "print", 
                      default = False,
                      help = "print all numbers up to N")
    
    (options, args) = parser.parse_args()
    if (options.num == None):
            print (parser.usage)
            exit(0)
    else:
            number = options.num
        
    # function calling
    result = table(number, options.print)
    
    print ("The " + str(number)+ "th table is " + str(result))

    if (options.out != None):
        # open a file in append mode
        f = open(options.out,"a")
        
        # write in the file
        f.write(str(result) + '\n')

# Driver code
if __name__ == '__main__':
    
    # function calling
    Main()