Question

I’m very new to python. I wish I could implement the command-line arg passing in python as my first python script. I have written this code:

def main(argv):
    try:
        opts, args = getopt.getopt(argv, "hb:b:f", ["help", "bucket=", "folder"])
    except getopt.GetoptError:
        usage()
        sys.exit(2)
    s3 = get_files()
    for opt, arg in opts:
        if opt in ("-h", "--help"):
            usage()
            sys.exit()
        elif opt in ("-b", "--bucket"):
            s3.bucketname = arg
        elif opt in ("-f", "--folder"):
            s3.foldername = arg
            print("Came here" + s3.foldername)
    s3.download_files()

In the -f argument from command is where I’m facing the problem. For debugging I used the print statement. I pass the arguments like this:

./hello -b something -f /path

but sadly it prints out:

Came here

But the foldername attribute is not getting assigned any value. Where I’m making the mistake?

Thanks in advance.

Answer 1

Argparse really is a much simpler way of solving problems like this

import argparse

if __name__ == "__main__":
    parser = argparse.ArgumentParser()
    parser.add_argument('-b', '--bucket', dest='bucketname', action='store')
    parser.add_argument('-f', '--folder', dest='folder', action='store')
    args = parser.parse_args('-b foo'.split())
    print args
    args = parser.parse_args('-b foo -f /foo'.split())
    print args

Gives:

> Namespace(bucketname='foo', folder=None)
> Namespace(bucketname='foo', folder='/foo')

Which means you could rewrite your function as:

import sys
import argparse

def main():
    parser = argparse.ArgumentParser()
    parser.add_argument('-b', '--bucket', dest='bucketname', action='store')
    parser.add_argument('-f', '--folder', dest='folder', action='store')
    args = parser.parse_args()
    s3 = get_files()
    s3.foldername = args.folder
    s3.download_files()

Without any further work, the output of script.py --help is:

usage: script.py [-h] [-b BUCKETNAME] [-f FOLDER]

optional arguments:
  -h, --help            show this help message and exit
  -b BUCKETNAME, --bucket BUCKETNAME
  -f FOLDER, --folder FOLDE