config.py

class Config(dict):
    def __init__(self, root_path, defaults=None):
        dict.__init__(self, defaults or {})
        self.root_path = root_path

    def from_envvar(self, variable_name, silent=False):
        """Loads a configuration from an environment variable pointing to
        a configuration file.  This is basically just a shortcut with nicer
        error messages for this line of code::

            app.config.from_pyfile(os.environ['YOURAPPLICATION_SETTINGS'])

        :param variable_name: name of the environment variable
        :param silent: set to ``True`` if you want silent failure for missing
                       files.
        :return: bool. ``True`` if able to load config, ``False`` otherwise.
        """
        rv = os.environ.get(variable_name)
        if not rv:
            if silent:
                return False
            raise RuntimeError(
                "The environment variable %r is not set "
                "and as such configuration could not be "
                "loaded.  Set this variable and make it "
                "point to a configuration file" % variable_name
            )
        return self.from_pyfile(rv, silent=silent)

    def from_pyfile(self, filename, silent=False):
        """Updates the values in the config from a Python file.  This function
        behaves as if the file was imported as module with the
        :meth:`from_object` function.

        :param filename: the filename of the config.  This can either be an
                         absolute filename or a filename relative to the
                         root path.
        :param silent: set to ``True`` if you want silent failure for missing
                       files.
        """
        filename = os.path.join(self.root_path, filename)
        d = types.ModuleType("config")
        d.__file__ = filename
        try:
            with open(filename, mode="rb") as config_file:
                exec(compile(config_file.read(), filename, "exec"), d.__dict__)
        except IOError as e:
            if silent and e.errno in (errno.ENOENT, errno.EISDIR, errno.ENOTDIR):
                return False
            e.strerror = "Unable to load configuration file (%s)" % e.strerror
            raise
        self.from_object(d)
        return True

    def from_object(self, obj):
        """Updates the values from the given object.  An object can be of one
        of the following two types:

        -   a string: in this case the object with that name will be imported
        -   an actual object reference: that object is used directly

        Objects are usually either modules or classes. :meth:`from_object`
        loads only the uppercase attributes of the module/class. A ``dict``
        object will not work with :meth:`from_object` because the keys of a
        ``dict`` are not attributes of the ``dict`` class.

        Example of module-based configuration::

            app.config.from_object('yourapplication.default_config')
            from yourapplication import default_config
            app.config.from_object(default_config)

        Nothing is done to the object before loading. If the object is a
        class and has ``@property`` attributes, it needs to be
        instantiated before being passed to this method.

        You should not use this function to load the actual configuration but
        rather configuration defaults.  The actual config should be loaded
        with :meth:`from_pyfile` and ideally from a location not within the
        package because the package might be installed system wide.

        See :ref:`config-dev-prod` for an example of class-based configuration
        using :meth:`from_object`.

        :param obj: an import name or object
        """
        if isinstance(obj, string_types):
            obj = import_string(obj)
        for key in dir(obj):
            if key.isupper():
                self[key] = getattr(obj, key)

    def from_file(self, filename, load, silent=False):
        """Update the values in the config from a file that is loaded
        using the ``load`` parameter. The loaded data is passed to the
        :meth:`from_mapping` method.
        :param filename: The path to the data file. This can be an
            absolute path or relative to the config root path.
        :param load: A callable that takes a file handle and returns a
            mapping of loaded data from the file.
        :type load: ``Callable[[Reader], Mapping]`` where ``Reader``
            implements a ``read`` method.
        :param silent: Ignore the file if it doesn't exist.
        """
        filename = os.path.join(self.root_path, filename)

        try:
            with open(filename) as f:
                obj = load(f)
        except IOError as e:
            if silent and e.errno in (errno.ENOENT, errno.EISDIR):
                return False

            e.strerror = "Unable to load configuration file (%s)" % e.strerror
            raise

        return self.from_mapping(obj)

    def from_json(self, filename, silent=False):
        """Update the values in the config from a JSON file. The loaded
        data is passed to the :meth:`from_mapping` method.

        :param filename: The path to the JSON file. This can be an
            absolute path or relative to the config root path.
        :param silent: Ignore the file if it doesn't exist.
        """
        warnings.warn(
            "'from_json' is deprecated and will be removed in 2.0."
            " Use 'from_file(filename, load=json.load)' instead.",
            DeprecationWarning,
            stacklevel=2,
        )
        from .json import load

        return self.from_file(filename, load, silent=silent)

    def from_mapping(self, *mapping, **kwargs):
        mappings = []
        if len(mapping) == 1:
            if hasattr(mapping[0], "items"):
                mappings.append(mapping[0].items())
            else:
                mappings.append(mapping[0])
        elif len(mapping) > 1:
            raise TypeError(
                "expected at most 1 positional argument, got %d" % len(mapping)
            )
        mappings.append(kwargs.items())
        for mapping in mappings:
            for (key, value) in mapping:
                if key.isupper():
                    self[key] = value
        return True

    def get_namespace(self, namespace, lowercase=True, trim_namespace=True):
        """Returns a dictionary containing a subset of configuration options
        that match the specified namespace/prefix. Example usage::

            app.config['IMAGE_STORE_TYPE'] = 'fs'
            app.config['IMAGE_STORE_PATH'] = '/var/app/images'
            app.config['IMAGE_STORE_BASE_URL'] = 'http://img.website.com'
            image_store_config = app.config.get_namespace('IMAGE_STORE_')

        The resulting dictionary `image_store_config` would look like::

            {
                'type': 'fs',
                'path': '/var/app/images',
                'base_url': 'http://img.website.com'
            }
        """
        rv = {}
        for k, v in iteritems(self):
            if not k.startswith(namespace):
                continue
            if trim_namespace:
                key = k[len(namespace) :]
            else:
                key = k
            if lowercase:
                key = key.lower()
            rv[key] = v
        return rv

    def __repr__(self):
        return "<%s %s>" % (self.__class__.__name__, dict.__repr__(self))