A starter template for a Python Command Line program

A starter template for a Python Command Line program

There are several ways to create a command line program in Python.

This blog post presents a simple example 'template' based around the built-in optparse module (with OptionParser class). The optparse module has good documentation on how to set it up, but seems to lack a few examples of how to actually use it.

You can copy-paste this code and edit it to suit your particular command line program.

"""

main.py

TODO_DESCRIBE_WHAT_THIS_DOES.

"""

import sys

from optparse import OptionParser

# usage() - prints out the usage text, from the top of this file :-) and the options

def usage(parser):

    print(__doc__)

    parser.print_help()

# optparse - parse the args

parser = OptionParser(

    usage="%prog <TODO_ARGS> [options]",

    version="0.1.0"

)

parser.add_option(

    "-i", "--input", metavar="INPUT_FILE", help="read data from INPUT_FILE", dest="input_file"

)

parser.add_option(

    "-l",

    "--language",

    dest="target_language",

    metavar="TARGET_LANGUAGE",  # 'metavar' helps make 'help' messages refer to values and is used to build the help for this option.

    default="English",

    help="translate to the target output language TARGET_LANGUAGE. Example: English.",

)

parser.add_option(

    "-o",

    "--output",

    dest="output_dir",

    default=None,

    help="the output directory. By default is None, so output is to stdout (no files are output).",

)

parser.add_option(

    "-v", "--verbose",  action='store_true', help="turn on verbose mode", dest="is_verbose"

)

(options, args) = parser.parse_args()

if len(args) != 1:

    usage(parser)

    sys.exit(2)

first_arg = args[0]

target_language = options.target_language

path_to_output_dir = None

if options.output_dir:

    path_to_output_dir = options.output_dir

Running python main.py will output help text like:

main.py

TODO_DESCRIBE_WHAT_THIS_DOES.

Usage: main.py <TODO_ARGS> [options]

Options:

  --version             show program's version number and exit

  -h, --help            show this help message and exit

  -i INPUT_FILE, --input=INPUT_FILE

                        read data from INPUT_FILE

  -l TARGET_LANGUAGE, --language=TARGET_LANGUAGE

                        translate to the target output language

                        TARGET_LANGUAGE. Example: English.

  -o OUTPUT_DIR, --output=OUTPUT_DIR

                        the output directory. By default is None, so output is

                        to stdout (no files are output).

  -v, --verbose         turn on verbose mode