• parser.add_subparsers()

  parser = subparsers.add_parser()

• parser.set_defaults(func=...)

Really bloody useful for parsing command line options given to scripts with ease!

import argparse

parser = argparse.ArgumentParser(description="Describe your program here")
# Define arguments
args = parser.parse_args()

You can add_argument()'s to the parser. Arguments can be positional or optional.Optional arguments are generally specified as a short command, e.g. -h, and/or as a long command, e.g. --help along with an action to perform if the command is received. Positional arguments are just defined as a name with no preceeding hypenated prefix.

For example, to add version information to the command line you could do:

parser.add_argument( "-v", "--version"
                   , action   = 'version'
                   , version  = '%(prog)s {version}'.format(version=__version__)
                   , help     = ("print version information")
                   )

If you want to store the value of an argument in some way you will want to use one of the following actions (there are more possibilities - see the Python docs):

• store

  To store a conditional you would do something like this:

  parser.add_argument("-j", "--jehtech", action="store")
  args = parser.parse_args() 
  print args.jehtech

  If you then ran your program with the command line argument python prog.py --jehtech "Hi JehTech" the variable args.jehtech would hold the string "Hi JehTech"

  To store a positional you would do something like this:

  parser.add_argument("jehtech_positional")
  args = parser.parse_args() 
  print args.jehtech_positional

  If you want your program as python prog.py "Hi positional" the variable args.jehtech_positional would hold the string "Hi positional".

• store_const (and store_true/store_false)

  Use these to store the presense of a flag that has no value associated with it. For example, a verbose flag, probably stands alone, i.e., the flag doesn't have a value associated with it. The const value is what is stored in the parser variable.

  parser.add_argument( "-T", "--test_mode"
                     , const    = "This the value to store"
                     , action   = 'store_const'
                     )
  args = parser.parse_args()

  If the option is specified on the command line the property args.test_mode will contain the string "This is the value to store". If it was not specified the property will be None.

  You can specify a default value to be stored if the option is not specified on the command line using the default=... argument to add_argument().

  parser.add_argument( "-T", "--test_mode"
                     , const    = "This the value to store"
                     , default  = "Default value if --test_mode not specified"
                     , action   = 'store_const'
                     )
  args = parser.parse_args()

  The actions store_true and store_false are just shorthand actions for when you would normally set const to either True or False.

  I.e.,

  parser.add_argument( "-T", "--test_mode"
                     , const    = True
                     , action   = 'store_const'
                     )

  Is equivalent to...

  parser.add_argument( "-T", "--test_mode", action="store_true")

• append

  This will append values to a list. See Python docs...