ArgParse

Many people use Python’s argparse command line argument parser. This parser can handle sub-commands like git commit -m "message" where commit is a sub-command and -m <message> is an argument of this sub-command parser. It’s possible to assign a callback function to each individual sub-command parser.

Advantages

Declarative description instead of imperative form.
All options from argparse can be used.
Declare accepted command-line arguments close to the responsible handler method
Complex parsers can be distributed accross multiple classes and merged via multiple inheritance.
Pre-defined argument templates like switch parameters (--help).

Comparison

pyTooling.Attributes.ArgParse

class Program:
  @DefaultHandler()
  @FlagArgument(short="-v", long="--verbose", dest="verbose", help="Show verbose messages.")
  def HandleDefault(self, args) -> None:
    pass

  @CommandHandler("new-user", help="Add a new user.")
  @StringArgument(dest="username", metaName="username", help="Name of the new user.")
  @LongValuedFlag("--quota", dest="quota", help="Max usable disk space.")
  def NewUserHandler(self, args) -> None:
    pass

  @CommandHandler("delete-user", help="Delete a user.")
  @StringArgument(dest="username", metaName="username", help="Name of the user.")
  @FlagArgument(short="-f", long="--force", dest="force", help="Ignore internal checks.")
  def DeleteUserHandler(self, args) -> None:
    pass

  @CommandHandler("list-user", help="List all users.")
  def ListUserHandler(self, args) -> None:
    pass

Traditional ArgParse

class Program:
  def __init__(self):
    mainParser = argparse.ArgumentParser()
    mainParser.set_defaults(func=self.HandleDefault)
    mainParser.add_argument("-v", "--verbose")
    subParsers = mainParser.add_subparsers()

    newUserParser = subParsers.add_parser("new-user", help="Add a new user.")
    newUserParser.add_argument(dest="username", metaName="username", help="Name of the new user.")
    newUserParser.add_argument("--quota", dest="quota", help="Max usable disk space.")
    newUserParser.set_defaults(func=self.NewUserHandler)

    deleteUserParser = subParsers.add_parser("delete-user", help="Delete a user.")
    deleteUserParser.add_argument(dest="username", metaName="username", help="Name of the user.")
    deleteUserParser.add_argument("-f", "--force", dest="force", help="Ignore internal checks.")
    deleteUserParser.set_defaults(func=self.DeleteUserHandler)

    listUserParser = subParsers.add_parser("list-user", help="List all users.")
    listUserParser.set_defaults(func=self.ListUserHandler)

  def HandleDefault(self, args) -> None:
    pass

  def NewUserHandler(self, args) -> None:
    pass

  def DeleteUserHandler(self, args) -> None:
    pass

  def ListUserHandler(self, args) -> None:
    pass

Arguments

Flags

ValuedFlags

ValuedTupleFlags

Argument Lists

Commands

Grouping Arguments

Split Handlers into multiple classes

Classic `argparse` Example

New `pyTooling.Attributes` Approach

A better and more descriptive solution could look like this:

Consumers

This package is used by:

✅ .
pyTooling.Attributes.ArgParse