config.py

"""
The config module holds package-wide configurables and provides
a uniform API for working with them.

Overview
========

This module supports the following requirements:
- options are referenced using keys in dot.notation, e.g. "x.y.option - z".
- keys are case-insensitive.
- functions should accept partial/regex keys, when unambiguous.
- options can be registered by modules at import time.
- options can be registered at init-time (via core.config_init)
- options have a default value, and (optionally) a description and
  validation function associated with them.
- options can be deprecated, in which case referencing them
  should produce a warning.
- deprecated options can optionally be rerouted to a replacement
  so that accessing a deprecated option reroutes to a differently
  named option.
- options can be reset to their default value.
- all option can be reset to their default value at once.
- all options in a certain sub - namespace can be reset at once.
- the user can set / get / reset or ask for the description of an option.
- a developer can register and mark an option as deprecated.
- you can register a callback to be invoked when the option value
  is set or reset. Changing the stored value is considered misuse, but
  is not verboten.

Implementation
==============

- Data is stored using nested dictionaries, and should be accessed
  through the provided API.

- "Registered options" and "Deprecated options" have metadata associated
  with them, which are stored in auxiliary dictionaries keyed on the
  fully-qualified key, e.g. "x.y.z.option".

- the config_init module is imported by the package's __init__.py file.
  placing any register_option() calls there will ensure those options
  are available as soon as pandas is loaded. If you use register_option
  in a module, it will only be available after that module is imported,
  which you should be aware of.

- `config_prefix` is a context_manager (for use with the `with` keyword)
  which can save developers some typing, see the docstring.

"""

from collections import namedtuple
from contextlib import contextmanager
import re
import warnings

import pandas.compat as compat
from pandas.compat import lmap, map, u

DeprecatedOption = namedtuple('DeprecatedOption', 'key msg rkey removal_ver')
RegisteredOption = namedtuple('RegisteredOption',
                              'key defval doc validator cb')

_deprecated_options = {}  # holds deprecated option metdata
_registered_options = {}  # holds registered option metdata
_global_config = {}  # holds the current values for registered options
_reserved_keys = ['all']  # keys which have a special meaning


class OptionError(AttributeError, KeyError):
    """Exception for pandas.options, backwards compatible with KeyError
    checks
    """

#
# User API


def _get_single_key(pat, silent):
    keys = _select_options(pat)
    if len(keys) == 0:
        if not silent:
            _warn_if_deprecated(pat)
        raise OptionError('No such keys(s): {pat!r}'.format(pat=pat))
    if len(keys) > 1:
        raise OptionError('Pattern matched multiple keys')
    key = keys[0]

    if not silent:
        _warn_if_deprecated(key)

    key = _translate_key(key)

    return key


def _get_option(pat, silent=False):
    key = _get_single_key(pat, silent)

    # walk the nested dict
    root, k = _get_root(key)
    return root[k]


def _set_option(*args, **kwargs):
    # must at least 1 arg deal with constraints later
    nargs = len(args)
    if not nargs or nargs % 2 != 0:
        raise ValueError("Must provide an even number of non-keyword "
                         "arguments")

    # default to false
    silent = kwargs.pop('silent', False)

    if kwargs:
        msg = '_set_option() got an unexpected keyword argument "{kwarg}"'
        raise TypeError(msg.format(list(kwargs.keys())[0]))

    for k, v in zip(args[::2], args[1::2]):
        key = _get_single_key(k, silent)

        o = _get_registered_option(key)
        if o and o.validator:
            o.validator(v)

        # walk the nested dict
        root, k = _get_root(key)
        root[k] = v

        if o.cb:
            if silent:
                with warnings.catch_warnings(record=True):
                    o.cb(key)
            else:
                o.cb(key)


def _describe_option(pat='', _print_desc=True):

    keys = _select_options(pat)
    if len(keys) == 0:
        raise OptionError('No such keys(s)')

    s = u('')
    for k in keys:  # filter by pat
        s += _build_option_description(k)

    if _print_desc:
        print(s)
    else:
        return s


def _reset_option(pat, silent=False):

    keys = _select_options(pat)

    if len(keys) == 0:
        raise OptionError('No such keys(s)')

    if len(keys) > 1 and len(pat) < 4 and pat != 'all':
        raise ValueError('You must specify at least 4 characters when '
                         'resetting multiple keys, use the special keyword '
                         '"all" to reset all the options to their default '
                         'value')

    for k in keys:
        _set_option(k, _registered_options[k].defval, silent=silent)


def get_default_val(pat):
    key = _get_single_key(pat, silent=True)
    return _get_registered_option(key).defval


class DictWrapper(object):
    """ provide attribute-style access to a nested dict"""

    def __init__(self, d, prefix=""):
        object.__setattr__(self, "d", d)
        object.__setattr__(self, "prefix", prefix)

    def __setattr__(self, key, val):
        prefix = object.__getattribute__(self, "prefix")
        if prefix:
            prefix += "."
        prefix += key
        # you can't set new keys
        # can you can't overwrite subtrees
        if key in self.d and not isinstance(self.d[key], dict):
            _set_option(prefix, val)
        else:
            raise OptionError("You can only set the value of existing options")

    def __getattr__(self, key):
        prefix = object.__getattribute__(self, "prefix")
        if prefix:
            prefix += "."
        prefix += key
        try:
            v = object.__getattribute__(self, "d")[key]
        except KeyError:
            raise OptionError("No such option")
        if isinstance(v, dict):
            return DictWrapper(v, prefix)
        else:
            return _get_option(prefix)

    def __dir__(self):
        return list(self.d.keys())

# For user convenience,  we'd like to have the available options described
# in the docstring. For dev convenience we'd like to generate the docstrings
# dynamically instead of maintaining them by hand. To this, we use the
# class below which wraps functions inside a callable, and converts
# __doc__ into a property function. The doctsrings below are templates
# using the py2.6+ advanced formatting syntax to plug in a concise list
# of options, and option descriptions.


class CallableDynamicDoc(object):

    def __init__(self, func, doc_tmpl):
        self.__doc_tmpl__ = doc_tmpl
        self.__func__ = func

    def __call__(self, *args, **kwds):
        return self.__func__(*args, **kwds)

    @property
    def __doc__(self):
        opts_desc = _describe_option('all', _print_desc=False)
        opts_list = pp_options_list(list(_registered_options.keys()))
        return self.__doc_tmpl__.format(opts_desc=opts_desc,
                                        opts_list=opts_list)


_get_option_tmpl = """
get_option(pat)

Retrieves the value of the specified option.

Available options:

{opts_list}

Parameters
----------
pat : str
    Regexp which should match a single option.
    Note: partial matches are supported for convenience, but unless you use the
    full option name (e.g. x.y.z.option_name), your code may break in future
    versions if new options with similar names are introduced.

Returns
-------
result : the value of the option

Raises
------
OptionError : if no such option exists

Notes
-----
The available options with its descriptions:

{opts_desc}
"""

_set_option_tmpl = """
set_option(pat, value)

Sets the value of the specified option.

Available options:

{opts_list}

Parameters
----------
pat : str
    Regexp which should match a single option.
    Note: partial matches are supported for convenience, but unless you use the
    full option name (e.g. x.y.z.option_name), your code may break in future
    versions if new options with similar names are introduced.
value :
    new value of option.

Returns
-------
None

Raises
------
OptionError if no such option exists

Notes
-----
The available options with its descriptions:

{opts_desc}
"""

_describe_option_tmpl = """
describe_option(pat, _print_desc=False)

Prints the description for one or more registered options.

Call with not arguments to get a listing for all registered options.

Available options:

{opts_list}

Parameters
----------
pat : str
    Regexp pattern. All matching keys will have their description displayed.
_print_desc : bool, default True
    If True (default) the description(s) will be printed to stdout.
    Otherwise, the description(s) will be returned as a unicode string
    (for testing).

Returns
-------
None by default, the description(s) as a unicode string if _print_desc
is False

Notes
-----
The available options with its descriptions:

{opts_desc}
"""

_reset_option_tmpl = """
reset_option(pat)

Reset one or more options to their default value.

Pass "all" as argument to reset all options.

Available options:

{opts_list}

Parameters
----------
pat : str/regex
    If specified only options matching `prefix*` will be reset.
    Note: partial matches are supported for convenience, but unless you
    use the full option name (e.g. x.y.z.option_name), your code may break
    in future versions if new options with similar names are introduced.

Returns
-------
None

Notes
-----
The available options with its descriptions:

{opts_desc}
"""

# bind the functions with their docstrings into a Callable
# and use that as the functions exposed in pd.api
get_option = CallableDynamicDoc(_get_option, _get_option_tmpl)
set_option = CallableDynamicDoc(_set_option, _set_option_tmpl)
reset_option = CallableDynamicDoc(_reset_option, _reset_option_tmpl)
describe_option = CallableDynamicDoc(_describe_option, _describe_option_tmpl)
options = DictWrapper(_global_config)

#
# Functions for use by pandas developers, in addition to User - api


class option_context(object):
    """
    Context manager to temporarily set options in the `with` statement context.

    You need to invoke as ``option_context(pat, val, [(pat, val), ...])``.

    Examples
    --------

    >>> with option_context('display.max_rows', 10, 'display.max_columns', 5):
    ...     ...
    """

    def __init__(self, *args):
        if not (len(args) % 2 == 0 and len(args) >= 2):
            raise ValueError('Need to invoke as'
                             ' option_context(pat, val, [(pat, val), ...]).')

        self.ops = list(zip(args[::2], args[1::2]))

    def __enter__(self):
        self.undo = [(pat, _get_option(pat, silent=True))
                     for pat, val in self.ops]

        for pat, val in self.ops:
            _set_option(pat, val, silent=True)

    def __exit__(self, *args):
        if self.undo:
            for pat, val in self.undo:
                _set_option(pat, val, silent=True)


def register_option(key, defval, doc='', validator=None, cb=None):
    """Register an option in the package-wide pandas config object

    Parameters
    ----------
    key       - a fully-qualified key, e.g. "x.y.option - z".
    defval    - the default value of the option
    doc       - a string description of the option
    validator - a function of a single argument, should raise `ValueError` if
                called with a value which is not a legal value for the option.
    cb        - a function of a single argument "key", which is called
                immediately after an option value is set/reset. key is
                the full name of the option.

    Returns
    -------
    Nothing.

    Raises
    ------
    ValueError if `validator` is specified and `defval` is not a valid value.

    """
    import tokenize
    import keyword
    key = key.lower()

    if key in _registered_options:
        msg = "Option '{key}' has already been registered"
        raise OptionError(msg.format(key=key))
    if key in _reserved_keys:
        msg = "Option '{key}' is a reserved key"
        raise OptionError(msg.format(key=key))

    # the default value should be legal
    if validator:
        validator(defval)

    # walk the nested dict, creating dicts as needed along the path
    path = key.split('.')

    for k in path:
        if not bool(re.match('^' + tokenize.Name + '$', k)):
            raise ValueError("{k} is not a valid identifier".format(k=k))
        if keyword.iskeyword(k):
            raise ValueError("{k} is a python keyword".format(k=k))

    cursor = _global_config
    msg = "Path prefix to option '{option}' is already an option"
    for i, p in enumerate(path[:-1]):
        if not isinstance(cursor, dict):
            raise OptionError(msg.format(option='.'.join(path[:i])))
        if p not in cursor:
            cursor[p] = {}
        cursor = cursor[p]

    if not isinstance(cursor, dict):
        raise OptionError(msg.format(option='.'.join(path[:-1])))

    cursor[path[-1]] = defval  # initialize

    # save the option metadata
    _registered_options[key] = RegisteredOption(key=key, defval=defval,
                                                doc=doc, validator=validator,
                                                cb=cb)


def deprecate_option(key, msg=None, rkey=None, removal_ver=None):
    """
    Mark option `key` as deprecated, if code attempts to access this option,
    a warning will be produced, using `msg` if given, or a default message
    if not.
    if `rkey` is given, any access to the key will be re-routed to `rkey`.

    Neither the existence of `key` nor that if `rkey` is checked. If they
    do not exist, any subsequence access will fail as usual, after the
    deprecation warning is given.

    Parameters
    ----------
    key - the name of the option to be deprecated. must be a fully-qualified
          option name (e.g "x.y.z.rkey").

    msg - (Optional) a warning message to output when the key is referenced.
          if no message is given a default message will be emitted.

    rkey - (Optional) the name of an option to reroute access to.
           If specified, any referenced `key` will be re-routed to `rkey`
           including set/get/reset.
           rkey must be a fully-qualified option name (e.g "x.y.z.rkey").
           used by the default message if no `msg` is specified.

    removal_ver - (Optional) specifies the version in which this option will
                  be removed. used by the default message if no `msg`
                  is specified.

    Returns
    -------
    Nothing

    Raises
    ------
    OptionError - if key has already been deprecated.

    """

    key = key.lower()

    if key in _deprecated_options:
        msg = "Option '{key}' has already been defined as deprecated."
        raise OptionError(msg.format(key=key))

    _deprecated_options[key] = DeprecatedOption(key, msg, rkey, removal_ver)

#
# functions internal to the module


def _select_options(pat):
    """returns a list of keys matching `pat`

    if pat=="all", returns all registered options
    """

    # short-circuit for exact key
    if pat in _registered_options:
        return [pat]

    # else look through all of them
    keys = sorted(_registered_options.keys())
    if pat == 'all':  # reserved key
        return keys

    return [k for k in keys if re.search(pat, k, re.I)]


def _get_root(key):
    path = key.split('.')
    cursor = _global_config
    for p in path[:-1]:
        cursor = cursor[p]
    return cursor, path[-1]


def _is_deprecated(key):
    """ Returns True if the given option has been deprecated """

    key = key.lower()
    return key in _deprecated_options


def _get_deprecated_option(key):
    """
    Retrieves the metadata for a deprecated option, if `key` is deprecated.

    Returns
    -------
    DeprecatedOption (namedtuple) if key is deprecated, None otherwise
    """

    try:
        d = _deprecated_options[key]
    except KeyError:
        return None
    else:
        return d


def _get_registered_option(key):
    """
    Retrieves the option metadata if `key` is a registered option.

    Returns
    -------
    RegisteredOption (namedtuple) if key is deprecated, None otherwise
    """
    return _registered_options.get(key)


def _translate_key(key):
    """
    if key id deprecated and a replacement key defined, will return the
    replacement key, otherwise returns `key` as - is
    """

    d = _get_deprecated_option(key)
    if d:
        return d.rkey or key
    else:
        return key


def _warn_if_deprecated(key):
    """
    Checks if `key` is a deprecated option and if so, prints a warning.

    Returns
    -------
    bool - True if `key` is deprecated, False otherwise.
    """

    d = _get_deprecated_option(key)
    if d:
        if d.msg:
            print(d.msg)
            warnings.warn(d.msg, FutureWarning)
        else:
            msg = "'{key}' is deprecated".format(key=key)
            if d.removal_ver:
                msg += (' and will be removed in {version}'
                        .format(version=d.removal_ver))
            if d.rkey:
                msg += ", please use '{rkey}' instead.".format(rkey=d.rkey)
            else:
                msg += ', please refrain from using it.'

            warnings.warn(msg, FutureWarning)
        return True
    return False


def _build_option_description(k):
    """ Builds a formatted description of a registered option and prints it """

    o = _get_registered_option(k)
    d = _get_deprecated_option(k)

    s = u('{k} ').format(k=k)

    if o.doc:
        s += '\n'.join(o.doc.strip().split('\n'))
    else:
        s += 'No description available.'

    if o:
        s += (u('\n    [default: {default}] [currently: {current}]')
              .format(default=o.defval, current=_get_option(k, True)))

    if d:
        s += u('\n    (Deprecated')
        s += (u(', use `{rkey}` instead.')
              .format(rkey=d.rkey if d.rkey else ''))
        s += u(')')

    s += '\n\n'
    return s


def pp_options_list(keys, width=80, _print=False):
    """ Builds a concise listing of available options, grouped by prefix """

    from textwrap import wrap
    from itertools import groupby

    def pp(name, ks):
        pfx = ('- ' + name + '.[' if name else '')
        ls = wrap(', '.join(ks), width, initial_indent=pfx,
                  subsequent_indent='  ', break_long_words=False)
        if ls and ls[-1] and name:
            ls[-1] = ls[-1] + ']'
        return ls

    ls = []
    singles = [x for x in sorted(keys) if x.find('.') < 0]
    if singles:
        ls += pp('', singles)
    keys = [x for x in keys if x.find('.') >= 0]

    for k, g in groupby(sorted(keys), lambda x: x[:x.rfind('.')]):
        ks = [x[len(k) + 1:] for x in list(g)]
        ls += pp(k, ks)
    s = '\n'.join(ls)
    if _print:
        print(s)
    else:
        return s

#
# helpers


@contextmanager
def config_prefix(prefix):
    """contextmanager for multiple invocations of API with a common prefix

    supported API functions: (register / get / set )__option

    Warning: This is not thread - safe, and won't work properly if you import
    the API functions into your module using the "from x import y" construct.

    Example:

    import pandas.core.config as cf
    with cf.config_prefix("display.font"):
        cf.register_option("color", "red")
        cf.register_option("size", " 5 pt")
        cf.set_option(size, " 6 pt")
        cf.get_option(size)
        ...

        etc'

    will register options "display.font.color", "display.font.size", set the
    value of "display.font.size"... and so on.
    """

    # Note: reset_option relies on set_option, and on key directly
    # it does not fit in to this monkey-patching scheme

    global register_option, get_option, set_option, reset_option

    def wrap(func):
        def inner(key, *args, **kwds):
            pkey = '{prefix}.{key}'.format(prefix=prefix, key=key)
            return func(pkey, *args, **kwds)

        return inner

    _register_option = register_option
    _get_option = get_option
    _set_option = set_option
    set_option = wrap(set_option)
    get_option = wrap(get_option)
    register_option = wrap(register_option)
    yield None
    set_option = _set_option
    get_option = _get_option
    register_option = _register_option

# These factories and methods are handy for use as the validator
# arg in register_option


def is_type_factory(_type):
    """

    Parameters
    ----------
    `_type` - a type to be compared against (e.g. type(x) == `_type`)

    Returns
    -------
    validator - a function of a single argument x , which raises
                ValueError if type(x) is not equal to `_type`

    """

    def inner(x):
        if type(x) != _type:
            msg = "Value must have type '{typ!s}'"
            raise ValueError(msg.format(typ=_type))

    return inner


def is_instance_factory(_type):
    """

    Parameters
    ----------
    `_type` - the type to be checked against

    Returns
    -------
    validator - a function of a single argument x , which raises
                ValueError if x is not an instance of `_type`

    """
    if isinstance(_type, (tuple, list)):
        _type = tuple(_type)
        from pandas.io.formats.printing import pprint_thing
        type_repr = "|".join(map(pprint_thing, _type))
    else:
        type_repr = "'{typ}'".format(typ=_type)

    def inner(x):
        if not isinstance(x, _type):
            msg = "Value must be an instance of {type_repr}"
            raise ValueError(msg.format(type_repr=type_repr))

    return inner


def is_one_of_factory(legal_values):

    callables = [c for c in legal_values if callable(c)]
    legal_values = [c for c in legal_values if not callable(c)]

    def inner(x):
        from pandas.io.formats.printing import pprint_thing as pp
        if x not in legal_values:

            if not any(c(x) for c in callables):
                pp_values = pp("|".join(lmap(pp, legal_values)))
                msg = "Value must be one of {pp_values}"
                if len(callables):
                    msg += " or a callable"
                raise ValueError(msg.format(pp_values=pp_values))

    return inner


# common type validators, for convenience
# usage: register_option(... , validator = is_int)
is_int = is_type_factory(int)
is_bool = is_type_factory(bool)
is_float = is_type_factory(float)
is_str = is_type_factory(str)
is_unicode = is_type_factory(compat.text_type)
is_text = is_instance_factory((str, bytes))


def is_callable(obj):
    """

    Parameters
    ----------
    `obj` - the object to be checked

    Returns
    -------
    validator - returns True if object is callable
        raises ValueError otherwise.

    """
    if not callable(obj):
        raise ValueError("Value must be a callable")
    return True