# Author: Steven J. Bethard <steven.bethard@gmail.com>.
"""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')
'integers', metavar='int', nargs='+', type=int,
help='an integer to be summed')
'--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))
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 may
be 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
All other classes in this module are considered implementation details.
(Also note that HelpFormatter and RawDescriptionHelpFormatter are only
considered public as object names -- the API of the formatter objects is
still considered an implementation detail.)
'ArgumentDefaultsHelpFormatter',
'RawDescriptionHelpFormatter',
'MetavarTypeHelpFormatter',
import collections as _collections
import textwrap as _textwrap
from gettext import gettext as _, ngettext
SUPPRESS = '==SUPPRESS=='
_UNRECOGNIZED_ARGS_ATTR = '_unrecognized_args'
# =============================
# Utility functions and classes
# =============================
class _AttributeHolder(object):
"""Abstract base class that provides __repr__.
The __repr__ method returns a string in the format::
ClassName(attr=name, attr=name, ...)
The attributes are determined either by a class-level attribute,
'_kwarg_names', or by inspecting the instance __dict__.
type_name = type(self).__name__
for arg in self._get_args():
arg_strings.append(repr(arg))
for name, value in self._get_kwargs():
arg_strings.append('%s=%r' % (name, value))
arg_strings.append('**%s' % repr(star_args))
return '%s(%s)' % (type_name, ', '.join(arg_strings))
return sorted(self.__dict__.items())
def _ensure_value(namespace, name, value):
if getattr(namespace, name, None) is None:
setattr(namespace, name, value)
return getattr(namespace, name)
class HelpFormatter(object):
"""Formatter for generating usage messages and argument help strings.
Only the name of this class is considered a public API. All the methods
provided by the class are considered an implementation detail.
# default setting for width
width = int(_os.environ['COLUMNS'])
except (KeyError, ValueError):
self._indent_increment = indent_increment
self._max_help_position = max_help_position
self._max_help_position = min(max_help_position,
max(width - 20, indent_increment * 2))
self._action_max_length = 0
self._root_section = self._Section(self, None)
self._current_section = self._root_section
self._whitespace_matcher = _re.compile(r'\s+', _re.ASCII)
self._long_break_matcher = _re.compile(r'\n\n\n+')
# ===============================
# Section and indentation methods
# ===============================
self._current_indent += self._indent_increment
self._current_indent -= self._indent_increment
assert self._current_indent >= 0, 'Indent decreased below 0.'
def __init__(self, formatter, parent, heading=None):
self.formatter = formatter
# format the indented section
if self.parent is not None:
join = self.formatter._join_parts
item_help = join([func(*args) for func, args in self.items])
if self.parent is not None:
# return nothing if the section was empty
# add the heading if the section was non-empty
if self.heading is not SUPPRESS and self.heading is not None:
current_indent = self.formatter._current_indent
heading = '%*s%s:\n' % (current_indent, '', self.heading)
# join the section-initial newline, the heading and the help
return join(['\n', heading, item_help, '\n'])
def _add_item(self, func, args):
self._current_section.items.append((func, args))
# ========================
# Message building methods
# ========================
def start_section(self, heading):
section = self._Section(self, self._current_section, heading)
self._add_item(section.format_help, [])
self._current_section = section
self._current_section = self._current_section.parent
def add_text(self, text):
if text is not SUPPRESS and text is not None:
self._add_item(self._format_text, [text])
def add_usage(self, usage, actions, groups, prefix=None):
if usage is not SUPPRESS:
args = usage, actions, groups, prefix
self._add_item(self._format_usage, args)
def add_argument(self, action):
if action.help is not SUPPRESS:
get_invocation = self._format_action_invocation
invocations = [get_invocation(action)]
for subaction in self._iter_indented_subactions(action):
invocations.append(get_invocation(subaction))
# update the maximum item length
invocation_length = max([len(s) for s in invocations])
action_length = invocation_length + self._current_indent
self._action_max_length = max(self._action_max_length,
# add the item to the list
self._add_item(self._format_action, [action])
def add_arguments(self, actions):
self.add_argument(action)
# =======================
# Help-formatting methods
# =======================
help = self._root_section.format_help()
help = self._long_break_matcher.sub('\n\n', help)
help = help.strip('\n') + '\n'
def _join_parts(self, part_strings):
if part and part is not SUPPRESS])
def _format_usage(self, usage, actions, groups, prefix):
# if usage is specified, use that
usage = usage % dict(prog=self._prog)
# if no optionals or positionals are available, usage is just prog
elif usage is None and not actions:
usage = '%(prog)s' % dict(prog=self._prog)
# if optionals and positionals are available, calculate usage
prog = '%(prog)s' % dict(prog=self._prog)
# split optionals from positionals
if action.option_strings:
positionals.append(action)
# build full usage string
format = self._format_actions_usage
action_usage = format(optionals + positionals, groups)
usage = ' '.join([s for s in [prog, action_usage] if s])
# wrap the usage parts if it's too long
text_width = self._width - self._current_indent
if len(prefix) + len(usage) > text_width:
# break usage into wrappable parts
opt_usage = format(optionals, groups)
pos_usage = format(positionals, groups)
opt_parts = _re.findall(part_regexp, opt_usage)
pos_parts = _re.findall(part_regexp, pos_usage)
assert ' '.join(opt_parts) == opt_usage
assert ' '.join(pos_parts) == pos_usage
# helper for wrapping lines
def get_lines(parts, indent, prefix=None):
line_len = len(prefix) - 1
line_len = len(indent) - 1
if line_len + 1 + len(part) > text_width and line:
lines.append(indent + ' '.join(line))
line_len = len(indent) - 1
line_len += len(part) + 1
lines.append(indent + ' '.join(line))
lines[0] = lines[0][len(indent):]
# if prog is short, follow it with optionals or positionals
if len(prefix) + len(prog) <= 0.75 * text_width:
indent = ' ' * (len(prefix) + len(prog) + 1)
lines = get_lines([prog] + opt_parts, indent, prefix)
lines.extend(get_lines(pos_parts, indent))
lines = get_lines([prog] + pos_parts, indent, prefix)
# if prog is long, put it on its own line
indent = ' ' * len(prefix)
parts = opt_parts + pos_parts
lines = get_lines(parts, indent)
lines.extend(get_lines(opt_parts, indent))
lines.extend(get_lines(pos_parts, indent))
return '%s%s\n\n' % (prefix, usage)
def _format_actions_usage(self, actions, groups):
# find group indices and identify actions in groups
start = actions.index(group._group_actions[0])
end = start + len(group._group_actions)
if actions[start:end] == group._group_actions:
for action in group._group_actions:
group_actions.add(action)
for i in range(start + 1, end):
# collect all actions format strings
for i, action in enumerate(actions):
# suppressed arguments are marked with None
# remove | separators for suppressed arguments
if action.help is SUPPRESS:
if inserts.get(i) == '|':
elif inserts.get(i + 1) == '|':
# produce all arg strings
elif not action.option_strings:
default = self._get_default_metavar_for_positional(action)
part = self._format_args(action, default)
# if it's in a group, strip the outer []
if action in group_actions:
if part[0] == '[' and part[-1] == ']':
# add the action string to the list
# produce the first way to invoke the option in brackets
option_string = action.option_strings[0]
# if the Optional doesn't take a value, format is:
part = '%s' % option_string
# if the Optional takes a value, format is:
default = self._get_default_metavar_for_optional(action)
args_string = self._format_args(action, default)
part = '%s %s' % (option_string, args_string)
# make it look optional if it's not required or in a group
if not action.required and action not in group_actions:
# add the action string to the list
# insert things at the necessary indices
for i in sorted(inserts, reverse=True):
parts[i:i] = [inserts[i]]
# join all the action items with spaces
text = ' '.join([item for item in parts if item is not None])
# clean up separators for mutually exclusive groups
text = _re.sub(r'(%s) ' % open, r'\1', text)
text = _re.sub(r' (%s)' % close, r'\1', text)
text = _re.sub(r'%s *%s' % (open, close), r'', text)
text = _re.sub(r'\(([^|]*)\)', r'\1', text)
def _format_text(self, text):
text = text % dict(prog=self._prog)
text_width = max(self._width - self._current_indent, 11)
indent = ' ' * self._current_indent
return self._fill_text(text, text_width, indent) + '\n\n'
def _format_action(self, action):
# determine the required width and the entry label
help_position = min(self._action_max_length + 2,
help_width = max(self._width - help_position, 11)
action_width = help_position - self._current_indent - 2
action_header = self._format_action_invocation(action)
It is recommended that you Edit text format, this type of Fix handles quite a lot in one request
