Question

I’m newbie to Python. I’d like to code a script running on Linux.
To test if user enter all the script arguments:

• If user type: myscript => print "Usage: myscript [Dir] [Old] [New]"
• If user type: myscript Dir => print "Please enter Old and New"
• If user type: myscript Dir Old => print "Please enter New"
• If user type all the required arguments, then execute the main().

How to code myscript?

Answer 1

#! /usr/bin/python3.2

import sys

if __name__ == '__main__':
    if len (sys.argv) < 4:
        print ( ['Usage: myscript [Dir] [Old] [New]',
            'Please enter Old and New',
            'Please enter New'] [len (sys.argv) - 1] )

Or you can use argparse. This will not do what you asked for in the question, but it will hopefully placate J.F. Sebastian.

#! /usr/bin/python3.2

import argparse

if __name__ == '__main__':
    p = argparse.ArgumentParser (description = 'What your program does.')
    p.add_argument ('dir', metavar = 'dir', type = str, help = 'The directory')
    p.add_argument ('old', metavar = 'old', type = str, help = 'The old value')
    p.add_argument ('new', metavar = 'new', type = str, help = 'The new value')
    args = p.parse_args ()