Python collections.Mapping() Examples

The following are 30 code examples for showing how to use collections.Mapping(). These examples are extracted from open source projects. You can vote up the ones you like or vote down the ones you don't like, and go to the original project or source file by following the links above each example.

You may want to check out the right sidebar which shows the related API usage.

You may also want to check out all available functions/classes of the module collections , or try the search function .

Example 1
Project: esmlab   Author: NCAR   File: config.py    License: Apache License 2.0 6 votes vote down vote up
def normalize_nested_keys(config):
    """ Replaces underscores with hyphens for keys for a nested Mapping

    Examples
    --------
    >>> a = {'x': 1, 'y_1': {'a_2': 2}}
    >>> normalize_nested_keys(a)
    {'x': 1, 'y-1': {'a-2': 2}}
    """
    config_norm = {}
    for key, value in config.items():
        if isinstance(value, Mapping):
            value = normalize_nested_keys(value)
        key_norm = normalize_key(key)
        config_norm[key_norm] = value

    return config_norm 
Example 2
Project: python-opencage-geocoder   Author: OpenCageData   File: geocoder.py    License: MIT License 6 votes vote down vote up
def floatify_latlng(input_value):
    """
    Work around a JSON dict with string, not float, lat/lngs.

    Given anything (list/dict/etc) it will return that thing again, *but* any
    dict (at any level) that has only 2 elements lat & lng, will be replaced
    with the lat & lng turned into floats.

    If the API returns the lat/lng as strings, and not numbers, then this
    function will 'clean them up' to be floats.
    """
    if isinstance(input_value, collections.Mapping):
        if len(input_value) == 2 and sorted(input_value.keys()) == ['lat', 'lng']:
            # This dict has only 2 keys 'lat' & 'lon'
            return {'lat': float_if_float(input_value["lat"]), 'lng': float_if_float(input_value["lng"])}
        else:
            return dict((key, floatify_latlng(value)) for key, value in input_value.items())
    elif isinstance(input_value, collections.MutableSequence):
        return [floatify_latlng(x) for x in input_value]
    else:
        return input_value 
Example 3
Project: jawfish   Author: war-and-code   File: _collections.py    License: MIT License 6 votes vote down vote up
def extend(self, *args, **kwargs):
        """Generic import function for any type of header-like object.
        Adapted version of MutableMapping.update in order to insert items
        with self.add instead of self.__setitem__
        """
        if len(args) > 1:
            raise TypeError("extend() takes at most 1 positional "
                            "arguments ({} given)".format(len(args)))
        other = args[0] if len(args) >= 1 else ()
        
        if isinstance(other, HTTPHeaderDict):
            for key, val in other.iteritems():
                self.add(key, val)
        elif isinstance(other, Mapping):
            for key in other:
                self.add(key, other[key])
        elif hasattr(other, "keys"):
            for key in other.keys():
                self.add(key, other[key])
        else:
            for key, value in other:
                self.add(key, value)

        for key, value in kwargs.items():
            self.add(key, value) 
Example 4
Project: django-accounting   Author: dulacp   File: foundation.py    License: MIT License 6 votes vote down vote up
def update(d, u, depth=-1):
    """
    Recursively merge or update dict-like objects.
    >>> update({'k1': {'k2': 2}}, {'k1': {'k2': {'k3': 3}}, 'k4': 4})
    {'k1': {'k2': {'k3': 3}}, 'k4': 4}
    """

    for k, v in u.iteritems():
        if isinstance(v, Mapping) and not depth == 0:
            r = update(d.get(k, {}), v, depth=max(depth - 1, -1))
            d[k] = r
        elif isinstance(d, Mapping):
            d[k] = u[k]
        else:
            d = {k: u[k]}
    return d 
Example 5
Project: gist-alfred   Author: danielecook   File: _collections.py    License: MIT License 6 votes vote down vote up
def extend(self, *args, **kwargs):
        """Generic import function for any type of header-like object.
        Adapted version of MutableMapping.update in order to insert items
        with self.add instead of self.__setitem__
        """
        if len(args) > 1:
            raise TypeError("extend() takes at most 1 positional "
                            "arguments ({0} given)".format(len(args)))
        other = args[0] if len(args) >= 1 else ()

        if isinstance(other, HTTPHeaderDict):
            for key, val in other.iteritems():
                self.add(key, val)
        elif isinstance(other, Mapping):
            for key in other:
                self.add(key, other[key])
        elif hasattr(other, "keys"):
            for key in other.keys():
                self.add(key, other[key])
        else:
            for key, value in other:
                self.add(key, value)

        for key, value in kwargs.items():
            self.add(key, value) 
Example 6
Project: gist-alfred   Author: danielecook   File: api_jwt.py    License: MIT License 6 votes vote down vote up
def encode(self, payload, key, algorithm='HS256', headers=None,
               json_encoder=None):
        # Check that we get a mapping
        if not isinstance(payload, Mapping):
            raise TypeError('Expecting a mapping object, as JWT only supports '
                            'JSON objects as payloads.')

        # Payload
        for time_claim in ['exp', 'iat', 'nbf']:
            # Convert datetime to a intDate value in known time-format claims
            if isinstance(payload.get(time_claim), datetime):
                payload[time_claim] = timegm(payload[time_claim].utctimetuple())

        json_payload = json.dumps(
            payload,
            separators=(',', ':'),
            cls=json_encoder
        ).encode('utf-8')

        return super(PyJWT, self).encode(
            json_payload, key, algorithm, headers, json_encoder
        ) 
Example 7
Project: respy   Author: OpenSourceEconomics   File: random_model.py    License: MIT License 6 votes vote down vote up
def _update_nested_dictionary(dict_, other):
    """Update a nested dictionary with another dictionary.

    The basic ``.update()`` method of dictionaries adds non-existing keys or replaces
    existing keys which works fine for unnested dictionaries. For nested dictionaries,
    levels under the current level are not updated but overwritten. This function
    recursively loops over keys and values and inserts the value if it is not a
    dictionary. If it is a dictionary, it applies the same process again.

    """
    for key, value in other.items():
        if isinstance(value, collections.Mapping):
            dict_[key] = _update_nested_dictionary(dict_.get(key, {}), value)
        else:
            dict_[key] = value
    return dict_ 
Example 8
Project: misp42splunk   Author: remg427   File: misc.py    License: GNU Lesser General Public License v3.0 6 votes vote down vote up
def execfile(filename, myglobals=None, mylocals=None):
        """
        Read and execute a Python script from a file in the given namespaces.
        The globals and locals are dictionaries, defaulting to the current
        globals and locals. If only globals is given, locals defaults to it.
        """
        if myglobals is None:
            # There seems to be no alternative to frame hacking here.
            caller_frame = inspect.stack()[1]
            myglobals = caller_frame[0].f_globals
            mylocals = caller_frame[0].f_locals
        elif mylocals is None:
            # Only if myglobals is given do we set mylocals to it.
            mylocals = myglobals
        if not isinstance(myglobals, Mapping):
            raise TypeError('globals must be a mapping')
        if not isinstance(mylocals, Mapping):
            raise TypeError('locals must be a mapping')
        with open(filename, "rbU") as fin:
             source = fin.read()
        code = compile(source, filename, "exec")
        exec_(code, myglobals, mylocals) 
Example 9
Project: misp42splunk   Author: remg427   File: misc.py    License: GNU Lesser General Public License v3.0 6 votes vote down vote up
def execfile(filename, myglobals=None, mylocals=None):
        """
        Read and execute a Python script from a file in the given namespaces.
        The globals and locals are dictionaries, defaulting to the current
        globals and locals. If only globals is given, locals defaults to it.
        """
        if myglobals is None:
            # There seems to be no alternative to frame hacking here.
            caller_frame = inspect.stack()[1]
            myglobals = caller_frame[0].f_globals
            mylocals = caller_frame[0].f_locals
        elif mylocals is None:
            # Only if myglobals is given do we set mylocals to it.
            mylocals = myglobals
        if not isinstance(myglobals, Mapping):
            raise TypeError('globals must be a mapping')
        if not isinstance(mylocals, Mapping):
            raise TypeError('locals must be a mapping')
        with open(filename, "rbU") as fin:
             source = fin.read()
        code = compile(source, filename, "exec")
        exec_(code, myglobals, mylocals) 
Example 10
Project: recipes-py   Author: luci   File: types.py    License: Apache License 2.0 6 votes vote down vote up
def thaw(obj):
  """Takes a a frozen object, and returns a mutable version of it.

  Conversions:
    * collections.Mapping -> dict
    * tuple -> list
    * frozenset -> set

  Close to the opposite of freeze().
  Does not convert dict keys.
  """
  if isinstance(obj, (dict, collections.OrderedDict, FrozenDict)):
    return {k: thaw(v) for k, v in obj.iteritems()}
  elif isinstance(obj, (list, tuple)):
    return [thaw(i) for i in obj]
  elif isinstance(obj, (set, frozenset)):
    return {thaw(i) for i in obj}
  else:
    return obj 
Example 11
Project: hierarchical_loc   Author: ethz-asl   File: tools.py    License: BSD 3-Clause "New" or "Revised" License 6 votes vote down vote up
def dict_update(d, u):
    """Improved update for nested dictionaries.

    Arguments:
        d: The dictionary to be updated.
        u: The update dictionary.

    Returns:
        The updated dictionary.
    """
    d = d.copy()
    for k, v in u.items():
        if isinstance(v, collections.Mapping):
            d[k] = dict_update(d.get(k, {}), v)
        else:
            d[k] = v
    return d 
Example 12
Project: core   Author: getavalon   File: _collections.py    License: MIT License 6 votes vote down vote up
def extend(self, *args, **kwargs):
        """Generic import function for any type of header-like object.
        Adapted version of MutableMapping.update in order to insert items
        with self.add instead of self.__setitem__
        """
        if len(args) > 1:
            raise TypeError("extend() takes at most 1 positional "
                            "arguments ({0} given)".format(len(args)))
        other = args[0] if len(args) >= 1 else ()

        if isinstance(other, HTTPHeaderDict):
            for key, val in other.iteritems():
                self.add(key, val)
        elif isinstance(other, Mapping):
            for key in other:
                self.add(key, other[key])
        elif hasattr(other, "keys"):
            for key in other.keys():
                self.add(key, other[key])
        else:
            for key, value in other:
                self.add(key, value)

        for key, value in kwargs.items():
            self.add(key, value) 
Example 13
Project: python-zhmcclient   Author: zhmcclient   File: _utils.py    License: Apache License 2.0 6 votes vote down vote up
def repr_dict(_dict, indent):
    """Return a debug representation of a dict or OrderedDict."""
    # pprint represents OrderedDict objects using the tuple init syntax,
    # which is not very readable. Therefore, dictionaries are iterated over.
    if _dict is None:
        return 'None'
    if not isinstance(_dict, Mapping):
        raise TypeError("Object must be a mapping, but is a %s" %
                        type(_dict))
    if isinstance(_dict, OrderedDict):
        kind = 'ordered'
        ret = '%s {\n' % kind  # non standard syntax for the kind indicator
        for key in six.iterkeys(_dict):
            value = _dict[key]
            ret += _indent('%r: %r,\n' % (key, value), 2)
    else:  # dict
        kind = 'sorted'
        ret = '%s {\n' % kind  # non standard syntax for the kind indicator
        for key in sorted(six.iterkeys(_dict)):
            value = _dict[key]
            ret += _indent('%r: %r,\n' % (key, value), 2)
    ret += '}'
    ret = repr_text(ret, indent=indent)
    return ret.lstrip(' ') 
Example 14
Project: ServerlessCrawler-VancouverRealState   Author: MarcelloLins   File: _collections.py    License: MIT License 6 votes vote down vote up
def extend(self, *args, **kwargs):
        """Generic import function for any type of header-like object.
        Adapted version of MutableMapping.update in order to insert items
        with self.add instead of self.__setitem__
        """
        if len(args) > 1:
            raise TypeError("extend() takes at most 1 positional "
                            "arguments ({0} given)".format(len(args)))
        other = args[0] if len(args) >= 1 else ()

        if isinstance(other, HTTPHeaderDict):
            for key, val in other.iteritems():
                self.add(key, val)
        elif isinstance(other, Mapping):
            for key in other:
                self.add(key, other[key])
        elif hasattr(other, "keys"):
            for key in other.keys():
                self.add(key, other[key])
        else:
            for key, value in other:
                self.add(key, value)

        for key, value in kwargs.items():
            self.add(key, value) 
Example 15
Project: ServerlessCrawler-VancouverRealState   Author: MarcelloLins   File: _collections.py    License: MIT License 6 votes vote down vote up
def extend(self, *args, **kwargs):
        """Generic import function for any type of header-like object.
        Adapted version of MutableMapping.update in order to insert items
        with self.add instead of self.__setitem__
        """
        if len(args) > 1:
            raise TypeError("extend() takes at most 1 positional "
                            "arguments ({0} given)".format(len(args)))
        other = args[0] if len(args) >= 1 else ()

        if isinstance(other, HTTPHeaderDict):
            for key, val in other.iteritems():
                self.add(key, val)
        elif isinstance(other, Mapping):
            for key in other:
                self.add(key, other[key])
        elif hasattr(other, "keys"):
            for key in other.keys():
                self.add(key, other[key])
        else:
            for key, value in other:
                self.add(key, value)

        for key, value in kwargs.items():
            self.add(key, value) 
Example 16
Project: plugin.video.emby   Author: MediaBrowser   File: _collections.py    License: GNU General Public License v3.0 6 votes vote down vote up
def extend(self, *args, **kwargs):
        """Generic import function for any type of header-like object.
        Adapted version of MutableMapping.update in order to insert items
        with self.add instead of self.__setitem__
        """
        if len(args) > 1:
            raise TypeError("extend() takes at most 1 positional "
                            "arguments ({0} given)".format(len(args)))
        other = args[0] if len(args) >= 1 else ()

        if isinstance(other, HTTPHeaderDict):
            for key, val in other.iteritems():
                self.add(key, val)
        elif isinstance(other, Mapping):
            for key in other:
                self.add(key, other[key])
        elif hasattr(other, "keys"):
            for key in other.keys():
                self.add(key, other[key])
        else:
            for key, value in other:
                self.add(key, value)

        for key, value in kwargs.items():
            self.add(key, value) 
Example 17
Project: aegea   Author: kislyuk   File: iam.py    License: Apache License 2.0 5 votes vote down vote up
def configure(args):
    for group, policies in config.managed_iam_groups.items():
        print("Creating group", group)
        formatted_policies = [(IAMPolicyBuilder(**p) if isinstance(p, collections.Mapping) else p) for p in policies]
        ensure_iam_group(group, policies=formatted_policies)
        msg = 'Created group {g}. Use the AWS console or "aws iam add-user-to-group --user-name USER --group-name {g}" to add users to it.' # noqa
        print(BOLD(msg.format(g=group))) 
Example 18
Project: dynamic-training-with-apache-mxnet-on-aws   Author: awslabs   File: utils.py    License: Apache License 2.0 5 votes vote down vote up
def namedtuple_with_defaults(typename, field_names, default_values=()):
    """ create a namedtuple with default values """
    T = collections.namedtuple(typename, field_names)
    T.__new__.__defaults__ = (None, ) * len(T._fields)
    if isinstance(default_values, collections.Mapping):
        prototype = T(**default_values)
    else:
        prototype = T(*default_values)
    T.__new__.__defaults__ = tuple(prototype)
    return T 
Example 19
Project: esmlab   Author: NCAR   File: config.py    License: Apache License 2.0 5 votes vote down vote up
def update(old, new, priority='new'):
    """ Update a nested dictionary with values from another
    This is like dict.update except that it smoothly merges nested values
    This operates in-place and modifies old
    Parameters
    ----------
    priority: string {'old', 'new'}
        If new (default) then the new dictionary has preference.
        Otherwise the old dictionary does.

    """

    for k, v in new.items():
        if k not in old and isinstance(v, Mapping):
            old[k] = {}
        if isinstance(v, Mapping):
            if old[k] is None:
                old[k] = {}

            update(old[k], v, priority=priority)

        else:
            if priority == 'new' or k not in old:
                old[k] = v

    return old 
Example 20
Project: esmlab   Author: NCAR   File: config.py    License: Apache License 2.0 5 votes vote down vote up
def expand_environment_variables(config):
    ''' Expand environment variables in a nested config dictionary

    This function will recursively search through any nested dictionaries
    and/or lists.

    Parameters
    ----------
    config : dict, iterable, or str
        Input object to search for environment variables

    Returns
    -------
    config : same type as input

    Examples
    --------
    >>> expand_environment_variables({'x': [1, 2, '$USER']})  # doctest: +SKIP
    {'x': [1, 2, 'my-username']}
    '''
    if isinstance(config, Mapping):
        return {k: expand_environment_variables(v) for k, v in config.items()}
    elif isinstance(config, str):
        return os.path.expanduser(os.path.expandvars(config))
    elif isinstance(config, (list, tuple, set)):
        return type(config)([expand_environment_variables(v) for v in config])
    else:
        return config 
Example 21
Project: jawfish   Author: war-and-code   File: _collections.py    License: MIT License 5 votes vote down vote up
def __eq__(self, other):
        if not isinstance(other, Mapping) and not hasattr(other, 'keys'):
            return False
        if not isinstance(other, type(self)):
            other = type(self)(other)
        return dict((k1, self[k1]) for k1 in self) == dict((k2, other[k2]) for k2 in other) 
Example 22
Project: jawfish   Author: war-and-code   File: structures.py    License: MIT License 5 votes vote down vote up
def __eq__(self, other):
        if isinstance(other, collections.Mapping):
            other = CaseInsensitiveDict(other)
        else:
            return NotImplemented
        # Compare insensitively
        return dict(self.lower_items()) == dict(other.lower_items())

    # Copy is required 
Example 23
Project: jawfish   Author: war-and-code   File: sessions.py    License: MIT License 5 votes vote down vote up
def merge_setting(request_setting, session_setting, dict_class=OrderedDict):
    """
    Determines appropriate setting for a given request, taking into account the
    explicit setting on that request, and the setting in the session. If a
    setting is a dictionary, they will be merged together using `dict_class`
    """

    if session_setting is None:
        return request_setting

    if request_setting is None:
        return session_setting

    # Bypass if not a dictionary (e.g. verify)
    if not (
            isinstance(session_setting, Mapping) and
            isinstance(request_setting, Mapping)
    ):
        return request_setting

    merged_setting = dict_class(to_key_val_list(session_setting))
    merged_setting.update(to_key_val_list(request_setting))

    # Remove keys that are set to None.
    for (k, v) in request_setting.items():
        if v is None:
            del merged_setting[k]

    merged_setting = dict((k, v) for (k, v) in merged_setting.items() if v is not None)

    return merged_setting 
Example 24
Project: jawfish   Author: war-and-code   File: utils.py    License: MIT License 5 votes vote down vote up
def to_key_val_list(value):
    """Take an object and test to see if it can be represented as a
    dictionary. If it can be, return a list of tuples, e.g.,

    ::

        >>> to_key_val_list([('key', 'val')])
        [('key', 'val')]
        >>> to_key_val_list({'key': 'val'})
        [('key', 'val')]
        >>> to_key_val_list('string')
        ValueError: cannot encode objects that are not 2-tuples.
    """
    if value is None:
        return None

    if isinstance(value, (str, bytes, bool, int)):
        raise ValueError('cannot encode objects that are not 2-tuples')

    if isinstance(value, collections.Mapping):
        value = value.items()

    return list(value)


# From mitsuhiko/werkzeug (used with permission). 
Example 25
Project: dataflow   Author: tensorpack   File: common.py    License: Apache License 2.0 5 votes vote down vote up
def _get_msg(self, dp):
        msg = [colored(u"datapoint %i/%i with %i components consists of" %
               (self.cnt, self.num, len(dp)), "cyan")]
        is_dict = isinstance(dp, Mapping)
        for k, entry in enumerate(dp):
            if is_dict:
                key, value = entry, dp[entry]
            else:
                key, value = k, entry
            msg.append(self._analyze_input_data(value, key, max_depth=self.max_depth, max_list=self.max_list))
        return u'\n'.join(msg) 
Example 26
Project: gist-alfred   Author: danielecook   File: _collections.py    License: MIT License 5 votes vote down vote up
def __eq__(self, other):
        if not isinstance(other, Mapping) and not hasattr(other, 'keys'):
            return False
        if not isinstance(other, type(self)):
            other = type(self)(other)
        return (dict((k.lower(), v) for k, v in self.itermerged()) ==
                dict((k.lower(), v) for k, v in other.itermerged())) 
Example 27
Project: gist-alfred   Author: danielecook   File: api_jws.py    License: MIT License 5 votes vote down vote up
def _load(self, jwt):
        if isinstance(jwt, text_type):
            jwt = jwt.encode('utf-8')

        if not issubclass(type(jwt), binary_type):
            raise DecodeError("Invalid token type. Token must be a {0}".format(
                binary_type))

        try:
            signing_input, crypto_segment = jwt.rsplit(b'.', 1)
            header_segment, payload_segment = signing_input.split(b'.', 1)
        except ValueError:
            raise DecodeError('Not enough segments')

        try:
            header_data = base64url_decode(header_segment)
        except (TypeError, binascii.Error):
            raise DecodeError('Invalid header padding')

        try:
            header = json.loads(header_data.decode('utf-8'))
        except ValueError as e:
            raise DecodeError('Invalid header string: %s' % e)

        if not isinstance(header, Mapping):
            raise DecodeError('Invalid header string: must be a json object')

        try:
            payload = base64url_decode(payload_segment)
        except (TypeError, binascii.Error):
            raise DecodeError('Invalid payload padding')

        try:
            signature = base64url_decode(crypto_segment)
        except (TypeError, binascii.Error):
            raise DecodeError('Invalid crypto padding')

        return (payload, signing_input, header, signature) 
Example 28
Project: gist-alfred   Author: danielecook   File: api_jwt.py    License: MIT License 5 votes vote down vote up
def decode(self, jwt, key='', verify=True, algorithms=None, options=None,
               **kwargs):

        if verify and not algorithms:
            warnings.warn(
                'It is strongly recommended that you pass in a ' +
                'value for the "algorithms" argument when calling decode(). ' +
                'This argument will be mandatory in a future version.',
                DeprecationWarning
            )

        payload, signing_input, header, signature = self._load(jwt)

        if options is None:
            options = {'verify_signature': verify}
        else:
            options.setdefault('verify_signature', verify)

        decoded = super(PyJWT, self).decode(
            jwt, key=key, algorithms=algorithms, options=options, **kwargs
        )

        try:
            payload = json.loads(decoded.decode('utf-8'))
        except ValueError as e:
            raise DecodeError('Invalid payload string: %s' % e)
        if not isinstance(payload, Mapping):
            raise DecodeError('Invalid payload string: must be a json object')

        if verify:
            merged_options = merge_dict(self.options, options)
            self._validate_claims(payload, merged_options, **kwargs)

        return payload 
Example 29
Project: verge3d-blender-addon   Author: Soft8Soft   File: misc.py    License: GNU General Public License v3.0 5 votes vote down vote up
def update(*args, **kwds):
        '''Like dict.update() but add counts instead of replacing them.

        Source can be an iterable, a dictionary, or another Counter instance.

        >>> c = Counter('which')
        >>> c.update('witch')           # add elements from another iterable
        >>> d = Counter('watch')
        >>> c.update(d)                 # add elements from another counter
        >>> c['h']                      # four 'h' in which, witch, and watch
        4

        '''
        # The regular dict.update() operation makes no sense here because the
        # replace behavior results in the some of original untouched counts
        # being mixed-in with all of the other counts for a mismash that
        # doesn't have a straight-forward interpretation in most counting
        # contexts.  Instead, we implement straight-addition.  Both the inputs
        # and outputs are allowed to contain zero and negative counts.

        if not args:
            raise TypeError("descriptor 'update' of 'Counter' object "
                            "needs an argument")
        self = args[0]
        args = args[1:]
        if len(args) > 1:
            raise TypeError('expected at most 1 arguments, got %d' % len(args))
        iterable = args[0] if args else None
        if iterable is not None:
            if isinstance(iterable, Mapping):
                if self:
                    self_get = self.get
                    for elem, count in iterable.items():
                        self[elem] = count + self_get(elem, 0)
                else:
                    super(Counter, self).update(iterable) # fast path when counter is empty
            else:
                _count_elements(self, iterable)
        if kwds:
            self.update(kwds) 
Example 30
Project: verge3d-blender-addon   Author: Soft8Soft   File: misc.py    License: GNU General Public License v3.0 5 votes vote down vote up
def subtract(*args, **kwds):
        '''Like dict.update() but subtracts counts instead of replacing them.
        Counts can be reduced below zero.  Both the inputs and outputs are
        allowed to contain zero and negative counts.

        Source can be an iterable, a dictionary, or another Counter instance.

        >>> c = Counter('which')
        >>> c.subtract('witch')             # subtract elements from another iterable
        >>> c.subtract(Counter('watch'))    # subtract elements from another counter
        >>> c['h']                          # 2 in which, minus 1 in witch, minus 1 in watch
        0
        >>> c['w']                          # 1 in which, minus 1 in witch, minus 1 in watch
        -1

        '''
        if not args:
            raise TypeError("descriptor 'subtract' of 'Counter' object "
                            "needs an argument")
        self = args[0]
        args = args[1:]
        if len(args) > 1:
            raise TypeError('expected at most 1 arguments, got %d' % len(args))
        iterable = args[0] if args else None
        if iterable is not None:
            self_get = self.get
            if isinstance(iterable, Mapping):
                for elem, count in iterable.items():
                    self[elem] = self_get(elem, 0) - count
            else:
                for elem in iterable:
                    self[elem] = self_get(elem, 0) - 1
        if kwds:
            self.subtract(kwds)