argparse — Parser for command-line options, arguments and subcommands
Added in version 3.2.
Source code: Lib/argparse.py
Note: While argparse is the default recommended standard library module for implementing basic command line applications, authors with more exacting requirements for exactly how their command line applications behave may find it doesn’t provide the necessary level of control. Refer to Choosing an argument parsing library for alternatives to consider when argparse doesn’t support behaviors that the application requires (such as entirely disabling support for interspersed options and positional arguments, or accepting option parameter values that start with - even when they correspond to another defined option).
The argparse module makes it easy to write user-friendly command-line interfaces. The program defines what arguments it requires, and argparse will figure out how to parse those out of sys.argv. The argparse module also automatically generates help and usage messages. The module will also issue errors when users give the program invalid arguments.
The argparse module’s support for command-line interfaces is built around an instance of argparse.ArgumentParser. It is a container for argument specifications and has options that apply to the parser as whole:
parser = argparse.ArgumentParser( prog='ProgramName', description='What the program does', epilog='Text at the bottom of help')
The ArgumentParser.add_argument() method attaches individual argument specifications to the parser. It supports positional arguments, options that accept values, and on/off flags:
parser.add_argument('filename') # positional argumentparser.add_argument('-c', '--count') # option that takes a valueparser.add_argument('-v', '--verbose', action='store_true') # on/off flag
The ArgumentParser.parse_args() method runs the parser and places the extracted data in a argparse.Namespace object: