CODEWITHSUNDEEP
pythoncommand-lineargumentsoptional-parameters
edesz
edesz

Reputation: 12406

Python commandline parameter not raising error if argument is wrongly used

I have the following Python code that has 1 command line optional parameter (c) that has an argument and 2 options (a and b) that do not have an argument:

import sys, getopt

def main(argv):
   inputfile = ''
   outputfile = ''
   try:
      opts, args = getopt.getopt(argv,"abc:",["csvfile="])
   except getopt.GetoptError:
      print 'Error in usage - a does not require an argument'
      sys.exit(2)
   for opt, arg in opts:
      print "Raw input is: {}" .format(opt)
      if opt in ("-c", "--csvfile"):
         outputfile = arg
         print 'Output file is {}' .format(outputfile)
      elif opt == '-a':
         print 'Alpha'
      elif opt == '-b':
         print 'Beta'
      print 'User choice is {}' .format(opt.lstrip('-'))

if __name__ == "__main__":
   main(sys.argv[1:])

When I enter python readwritestore.py -a I get:

Raw input is: -a
Alpha
User choice is a

This is what I was hoping for if the commandline argument is -a. However, if I enter python readwritestore.py -a csvfile_name, then I get:

Raw input is: -a
Alpha
User choice is a

This is not what I intended for. In this function, c is the only option that rquires an argument. If I enter a with an argument, the code should give the error message that I set up

Error in usage - a does not require an argument

This does not happen for a or b. It is allowing the argument to be entered without raising an error.

If the options that do not require an argument are entered with an argument, then I would like it to raise an error. python readwritestore.py -a text and python readwritestore.py -b text should raise the error Error in usage - a does not require an argument.

Is there a way to specify this? Is getopt() the correct way to do this?

Additional Information:

I only want python readwritestore.py -c text to work with the argument. For the other 2 options, a and b, the code should raise the error.

Upvotes: 0

Views: 1593

Answers (1)

pwnsauce
pwnsauce

Reputation: 414

checking the size of sys.argv (the list of argument supplied when calling the script) can help you checking that : 

import sys
import getopt


def main(argv):
    inputfile = ''
    outputfile = ''
    opts, args = getopt.getopt(argv, "abc:", ["csvfile="])
    for opt, arg in opts:
        print "Raw input is:", opt
        if opt in ("-c", "--csvfile"):
            outputfile = arg
            print 'Output file is ', outputfile
        elif opt == '-a':
            if len(sys.argv)=2:
                print 'Alpha'
            else:
                print "incorect number of argument"
        elif opt == '-b':
            if len(sys.argv)=2:
                print 'Beta'
            else:
                print "incorect number of argument"
        print 'User choice is ', opt

if __name__ == "__main__":
    main(sys.argv[1:])

I know it's not what you asked (argparse) but here is how you could do it with argparse :

from argparse import *

def main():
    parser = ArgumentParser()
    parser.add_argument('-c', '--csvfile', help='do smth with cvsfile')
    parser.add_argument(
        '-a', '--Alpha', help='Alpha', action='store_true')
    parser.add_argument(
        '-b', '--Beta', help='beta smth', action='store_true')
    if args.csvfile:
        print 'Output file is {}' .format(args.csvfile)
    if args.Alpha:
        print 'Alpha'
    if args.Beta:
        print 'Beta'

if __name__ == "__main__":
    main()

It will raise an error is to many argument are supplied. (also python readwritestore.py -h will display the help just like man in unix)

Upvotes: 1

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