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# Copyright 2009 Facebook
# Licensed under the Apache License, Version 2.0 (the "License"); you may
# not use this file except in compliance with the License. You may obtain
# a copy of the License at
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
# License for the specific language governing permissions and limitations
# under the License.
"""A command line parsing module that lets modules define their own options.
This module is inspired by Google's `gflags
<>`_. The primary difference
with libraries such as `argparse` is that a global registry is used so
that options may be defined in any module (it also enables
`tornado.log` by default). The rest of Tornado does not depend on this
module, so feel free to use `argparse` or other configuration
libraries if you prefer them.
Options must be defined with `tornado.options.define` before use,
generally at the top level of a module. The options are then
accessible as attributes of `tornado.options.options`::
# myapp/
from tornado.options import define, options
define("mysql_host", default="", help="Main user DB")
define("memcache_hosts", default="", multiple=True,
help="Main user memcache servers")
def connect():
db = database.Connection(options.mysql_host)
# myapp/
from tornado.options import define, options
define("port", default=8080, help="port to listen on")
def start_server():
app = make_app()
The ``main()`` method of your application does not need to be aware of all of
the options used throughout your program; they are all automatically loaded
when the modules are loaded. However, all modules that define options
must have been imported before the command line is parsed.
Your ``main()`` method can parse the command line or parse a config file with
either `parse_command_line` or `parse_config_file`::
import myapp.db, myapp.server
import tornado.options
if __name__ == '__main__':
# or
.. note::
When using multiple ``parse_*`` functions, pass ``final=False`` to all
but the last one, or side effects may occur twice (in particular,
this can result in log messages being doubled).
`tornado.options.options` is a singleton instance of `OptionParser`, and
the top-level functions in this module (`define`, `parse_command_line`, etc)
simply call methods on it. You may create additional `OptionParser`
instances to define isolated sets of options, such as for subcommands.
.. note::
By default, several options are defined that will configure the
standard `logging` module when `parse_command_line` or `parse_config_file`
are called. If you want Tornado to leave the logging configuration
alone so you can manage it yourself, either pass ``--logging=none``
on the command line or do the following to disable it in code::
from tornado.options import options, parse_command_line
options.logging = None
.. versionchanged:: 4.3
Dashes and underscores are fully interchangeable in option names;
options can be defined, set, and read with any mix of the two.
Dashes are typical for command-line usage while config files require
from __future__ import absolute_import, division, print_function
import datetime
import numbers
import re
import sys
import os
import textwrap
from tornado.escape import _unicode, native_str
from tornado.log import define_logging_options
from tornado import stack_context
from tornado.util import basestring_type, exec_in
class Error(Exception):
"""Exception raised by errors in the options module."""
class OptionParser(object):
"""A collection of options, a dictionary with object-like access.
Normally accessed via static functions in the `tornado.options` module,
which reference a global instance.
def __init__(self):
# we have to use self.__dict__ because we override setattr.
self.__dict__['_options'] = {}
self.__dict__['_parse_callbacks'] = []
self.define("help", type=bool, help="show this help information",
def _normalize_name(self, name):
return name.replace('_', '-')
def __getattr__(self, name):
name = self._normalize_name(name)
if isinstance(self._options.get(name), _Option):
return self._options[name].value()
raise AttributeError("Unrecognized option %r" % name)
def __setattr__(self, name, value):
name = self._normalize_name(name)
if isinstance(self._options.get(name), _Option):
return self._options[name].set(value)
raise AttributeError("Unrecognized option %r" % name)
def __iter__(self):
return ( for opt in self._options.values())
def __contains__(self, name):
name = self._normalize_name(name)
return name in self._options
def __getitem__(self, name):
return self.__getattr__(name)
def __setitem__(self, name, value):
return self.__setattr__(name, value)
def items(self):
"""A sequence of (name, value) pairs.
.. versionadded:: 3.1
return [(, opt.value()) for name, opt in self._options.items()]
def groups(self):
"""The set of option-groups created by ``define``.
.. versionadded:: 3.1
return set(opt.group_name for opt in self._options.values())
def group_dict(self, group):
"""The names and values of options in a group.
Useful for copying options into Application settings::
from tornado.options import define, parse_command_line, options
define('template_path', group='application')
define('static_path', group='application')
application = Application(
handlers, **options.group_dict('application'))
.. versionadded:: 3.1
return dict(
(, opt.value()) for name, opt in self._options.items()
if not group or group == opt.group_name)
def as_dict(self):
"""The names and values of all options.
.. versionadded:: 3.1
return dict(
(, opt.value()) for name, opt in self._options.items())
def define(self, name, default=None, type=None, help=None, metavar=None,
multiple=False, group=None, callback=None):
"""Defines a new command line option.
``type`` can be any of `str`, `int`, `float`, `bool`,
`~datetime.datetime`, or `~datetime.timedelta`. If no ``type``
is given but a ``default`` is, ``type`` is the type of
``default``. Otherwise, ``type`` defaults to `str`.
If ``multiple`` is True, the option value is a list of ``type``
instead of an instance of ``type``.
``help`` and ``metavar`` are used to construct the
automatically generated command line help string. The help
message is formatted like::
--name=METAVAR help string
``group`` is used to group the defined options in logical
groups. By default, command line options are grouped by the
file in which they are defined.
Command line option names must be unique globally.
If a ``callback`` is given, it will be run with the new value whenever
the option is changed. This can be used to combine command-line
and file-based options::
define("config", type=str, help="path to config file",
callback=lambda path: parse_config_file(path, final=False))
With this definition, options in the file specified by ``--config`` will
override options set earlier on the command line, but can be overridden
by later flags.
normalized = self._normalize_name(name)
if normalized in self._options:
raise Error("Option %r already defined in %s" %
(normalized, self._options[normalized].file_name))
frame = sys._getframe(0)
options_file = frame.f_code.co_filename
# Can be called directly, or through top level define() fn, in which
# case, step up above that frame to look for real caller.
if (frame.f_back.f_code.co_filename == options_file and
frame.f_back.f_code.co_name == 'define'):
frame = frame.f_back
file_name = frame.f_back.f_code.co_filename
if file_name == options_file:
file_name = ""
if type is None:
if not multiple and default is not None:
type = default.__class__
type = str
if group:
group_name = group
group_name = file_name
option = _Option(name, file_name=file_name,
default=default, type=type, help=help,
metavar=metavar, multiple=multiple,
self._options[normalized] = option
def parse_command_line(self, args=None, final=True):
"""Parses all options given on the command line (defaults to
Options look like ``--option=value`` and are parsed according
to their ``type``. For boolean options, ``--option`` is
equivalent to ``--option=true``
If the option has ``multiple=True``, comma-separated values
are accepted. For multi-value integer options, the syntax
``x:y`` is also accepted and equivalent to ``range(x, y)``.
Note that ``args[0]`` is ignored since it is the program name
in `sys.argv`.
We return a list of all arguments that are not parsed as options.
If ``final`` is ``False``, parse callbacks will not be run.
This is useful for applications that wish to combine configurations
from multiple sources.
if args is None:
args = sys.argv
remaining = []
for i in range(1, len(args)):
# All things after the last option are command line arguments
if not args[i].startswith("-"):
remaining = args[i:]
if args[i] == "--":
remaining = args[i + 1:]
arg = args[i].lstrip("-")
name, equals, value = arg.partition("=")
name = self._normalize_name(name)
if name not in self._options:
raise Error('Unrecognized command line option: %r' % name)
option = self._options[name]
if not equals:
if option.type == bool:
value = "true"
raise Error('Option %r requires a value' % name)
if final:
return remaining
def parse_config_file(self, path, final=True):
"""Parses and loads the config file at the given path.
The config file contains Python code that will be executed (so
it is **not safe** to use untrusted config files). Anything in
the global namespace that matches a defined option will be
used to set that option's value.
Options are not parsed from strings as they would be on the
command line; they should be set to the correct type (this
means if you have ``datetime`` or ``timedelta`` options you
will need to import those modules in the config file.
Example (using the options defined in the top-level docs of
this module)::
port = 80
mysql_host = ''
memcache_hosts = ['',
If ``final`` is ``False``, parse callbacks will not be run.
This is useful for applications that wish to combine configurations
from multiple sources.
.. note::
`tornado.options` is primarily a command-line library.
Config file support is provided for applications that wish
to use it, but applications that prefer config files may
wish to look at other libraries instead.
.. versionchanged:: 4.1
Config files are now always interpreted as utf-8 instead of
the system default encoding.
.. versionchanged:: 4.4
The special variable ``__file__`` is available inside config
files, specifying the absolute path to the config file itself.
config = {'__file__': os.path.abspath(path)}
with open(path, 'rb') as f:
exec_in(native_str(, config, config)
for name in config:
normalized = self._normalize_name(name)
if normalized in self._options:
if final:
def print_help(self, file=None):
"""Prints all the command line options to stderr (or another file)."""
if file is None:
file = sys.stderr
print("Usage: %s [OPTIONS]" % sys.argv[0], file=file)
print("\nOptions:\n", file=file)
by_group = {}
for option in self._options.values():
by_group.setdefault(option.group_name, []).append(option)
for filename, o in sorted(by_group.items()):
if filename:
print("\n%s options:\n" % os.path.normpath(filename), file=file)
o.sort(key=lambda option:
for option in o:
# Always print names with dashes in a CLI context.
prefix = self._normalize_name(
if option.metavar:
prefix += "=" + option.metavar
description = or ""
if option.default is not None and option.default != '':
description += " (default %s)" % option.default
lines = textwrap.wrap(description, 79 - 35)
if len(prefix) > 30 or len(lines) == 0:
lines.insert(0, '')
print(" --%-30s %s" % (prefix, lines[0]), file=file)
for line in lines[1:]:
print("%-34s %s" % (' ', line), file=file)
def _help_callback(self, value):
if value:
def add_parse_callback(self, callback):
"""Adds a parse callback, to be invoked when option parsing is done."""
def run_parse_callbacks(self):
for callback in self._parse_callbacks:
def mockable(self):
"""Returns a wrapper around self that is compatible with
`mock.patch <unittest.mock.patch>`.
The `mock.patch <unittest.mock.patch>` function (included in
the standard library `unittest.mock` package since Python 3.3,
or in the third-party ``mock`` package for older versions of
Python) is incompatible with objects like ``options`` that
override ``__getattr__`` and ``__setattr__``. This function
returns an object that can be used with `mock.patch.object
<unittest.mock.patch.object>` to modify option values::
with mock.patch.object(options.mockable(), 'name', value):
assert == value
return _Mockable(self)
class _Mockable(object):
"""`mock.patch` compatible wrapper for `OptionParser`.
As of ``mock`` version 1.0.1, when an object uses ``__getattr__``
hooks instead of ``__dict__``, ``patch.__exit__`` tries to delete
the attribute it set instead of setting a new one (assuming that
the object does not catpure ``__setattr__``, so the patch
created a new attribute in ``__dict__``).
_Mockable's getattr and setattr pass through to the underlying
OptionParser, and delattr undoes the effect of a previous setattr.
def __init__(self, options):
# Modify __dict__ directly to bypass __setattr__
self.__dict__['_options'] = options
self.__dict__['_originals'] = {}
def __getattr__(self, name):
return getattr(self._options, name)
def __setattr__(self, name, value):
assert name not in self._originals, "don't reuse mockable objects"
self._originals[name] = getattr(self._options, name)
setattr(self._options, name, value)
def __delattr__(self, name):
setattr(self._options, name, self._originals.pop(name))
class _Option(object):
UNSET = object()
def __init__(self, name, default=None, type=basestring_type, help=None,
metavar=None, multiple=False, file_name=None, group_name=None,
if default is None and multiple:
default = [] = name
self.type = type = help
self.metavar = metavar
self.multiple = multiple
self.file_name = file_name
self.group_name = group_name
self.callback = callback
self.default = default
self._value = _Option.UNSET
def value(self):
return self.default if self._value is _Option.UNSET else self._value
def parse(self, value):
_parse = {
datetime.datetime: self._parse_datetime,
datetime.timedelta: self._parse_timedelta,
bool: self._parse_bool,
basestring_type: self._parse_string,
}.get(self.type, self.type)
if self.multiple:
self._value = []
for part in value.split(","):
if issubclass(self.type, numbers.Integral):
# allow ranges of the form X:Y (inclusive at both ends)
lo, _, hi = part.partition(":")
lo = _parse(lo)
hi = _parse(hi) if hi else lo
self._value.extend(range(lo, hi + 1))
self._value = _parse(value)
if self.callback is not None:
return self.value()
def set(self, value):
if self.multiple:
if not isinstance(value, list):
raise Error("Option %r is required to be a list of %s" %
(, self.type.__name__))
for item in value:
if item is not None and not isinstance(item, self.type):
raise Error("Option %r is required to be a list of %s" %
(, self.type.__name__))
if value is not None and not isinstance(value, self.type):
raise Error("Option %r is required to be a %s (%s given)" %
(, self.type.__name__, type(value)))
self._value = value
if self.callback is not None:
# Supported date/time formats in our options
"%a %b %d %H:%M:%S %Y",
"%Y-%m-%d %H:%M:%S",
"%Y-%m-%d %H:%M",
"%Y%m%d %H:%M:%S",
"%Y%m%d %H:%M",
def _parse_datetime(self, value):
for format in self._DATETIME_FORMATS:
return datetime.datetime.strptime(value, format)
except ValueError:
raise Error('Unrecognized date/time format: %r' % value)
'h': 'hours',
'm': 'minutes',
'min': 'minutes',
's': 'seconds',
'sec': 'seconds',
'ms': 'milliseconds',
'us': 'microseconds',
'd': 'days',
'w': 'weeks',
_FLOAT_PATTERN = r'[-+]?(?:\d+(?:\.\d*)?|\.\d+)(?:[eE][-+]?\d+)?'
_TIMEDELTA_PATTERN = re.compile(
r'\s*(%s)\s*(\w*)\s*' % _FLOAT_PATTERN, re.IGNORECASE)
def _parse_timedelta(self, value):
sum = datetime.timedelta()
start = 0
while start < len(value):
m = self._TIMEDELTA_PATTERN.match(value, start)
if not m:
raise Exception()
num = float(
units = or 'seconds'
units = self._TIMEDELTA_ABBREV_DICT.get(units, units)
sum += datetime.timedelta(**{units: num})
start = m.end()
return sum
except Exception:
def _parse_bool(self, value):
return value.lower() not in ("false", "0", "f")
def _parse_string(self, value):
return _unicode(value)
options = OptionParser()
"""Global options object.
All defined options are available as attributes on this object.
def define(name, default=None, type=None, help=None, metavar=None,
multiple=False, group=None, callback=None):
"""Defines an option in the global namespace.
See `OptionParser.define`.
return options.define(name, default=default, type=type, help=help,
metavar=metavar, multiple=multiple, group=group,
def parse_command_line(args=None, final=True):
"""Parses global options from the command line.
See `OptionParser.parse_command_line`.
return options.parse_command_line(args, final=final)
def parse_config_file(path, final=True):
"""Parses global options from a config file.
See `OptionParser.parse_config_file`.
return options.parse_config_file(path, final=final)
def print_help(file=None):
"""Prints all the command line options to stderr (or another file).
See `OptionParser.print_help`.
return options.print_help(file)
def add_parse_callback(callback):
"""Adds a parse callback, to be invoked when option parsing is done.
See `OptionParser.add_parse_callback`
# Default options