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argparse.md

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@author : 7elmie

Module argparse

Command-line parsing library This module is an optparse-inspired command-line parsing library that:

-handles both optional and positional arguments
-produces highly informative usage messages
-supports parsers that dispatch to sub-parsers

The following is a simple usage example that sums integers from the command-line and writes the result to a file::

parser = argparse.ArgumentParser(description='sum the integers at the command line')
parser.add_argument('integers', metavar='int', nargs='+', type=int,help='an integer to be summed')
parser.add_argument('--log', default=sys.stdout, type=argparse.FileType('w'),help='the file where the sum should be written')
args = parser.parse_args()
args.log.write('%s' % sum(args.integers))
args.log.close()

The module contains the following public classes:

  • ArgumentParser -- The main entry point for command-line parsing. As the example above shows, the add_argument() method is used to populate the parser with actions for optional and positional arguments. Then the parse_args() method is invoked to convert the args at the command-line into an object with attributes.
  • ArgumentError -- The exception raised by ArgumentParser objects when there are errors with the parser's actions. Errors raised while parsing the command-line are caught by ArgumentParser and emitted as command-line messages.
  • FileType -- A factory for defining types of files to be created. As the example above shows, instances of FileType are typically passed as the type= argument of add_argument() calls.
  • Action -- The base class for parser actions.Typically actions are selected by passing strings like 'store_true' or 'append_const' to the action= argument of add_argument(). However, for greater customization of ArgumentParser actions, subclasses of Action maybe defined and passed as the action= argument.
  • HelpFormatter, RawDescriptionHelpFormatter, RawTextHelpFormatter,ArgumentDefaultsHelpFormatter -- Formatter classes which may be passed as the formatter_class= argument to the ArgumentParser constructor.
  • HelpFormatter is the default,RawDescriptionHelpFormatter and RawTextHelpFormatter tell the parser not to change the formatting for help text, and ArgumentDefaultsHelpFormatter adds information about argument defaults to the help.