flask源码笔记：三，app.py模块（4）——Flask的初始化之诸多属性

源代码：
    #: The class that is used for the :data:`~flask.g` instance.
    #:
    #: Example use cases for a custom class:
    #:
    #: 1. Store arbitrary attributes on flask.g.
    #: 2. Add a property for lazy per-request database connectors.
    #: 3. Return None instead of AttributeError on expected attributes.
    #: 4. Raise exception if an unexpected attr is set, a "controlled" flask.g.
    #:
    #: In Flask 0.9 this property was called `request_globals_class` but it
    #: was changed in 0.10 to :attr:`app_ctx_globals_class` because the
    #: flask.g object is not application context scoped.
    #:
    #: .. versionadded:: 0.10
    app_ctx_globals_class = _AppCtxGlobals
#设定flask.g的属性，可以看到它是一个类，通过其示例，可以自定义诸多的可用于整个app的字典到flask.g
#class _AppCtxGlobals(object):
#   """A plain object."""


#    def get(self, name, default=None):
#       return self.__dict__.get(name, default)


#    def __contains__(self, item):
#       return item in self.__dict__


#    def __iter__(self):
#       return iter(self.__dict__)


#    def __repr__(self):
#        top = _app_ctx_stack.top
#        if top is not None:
#            return '<flask.g of %r>' % top.app.name
#        return object.__repr__(self)


    # Backwards compatibility support
    def _get_request_globals_class(self):
        return self.app_ctx_globals_class
    def _set_request_globals_class(self, value):
        from warnings import warn
        warn(DeprecationWarning('request_globals_class attribute is now '
                                'called app_ctx_globals_class'))
        self.app_ctx_globals_class = value
    request_globals_class = property(_get_request_globals_class,
                                     _set_request_globals_class)
    del _get_request_globals_class, _set_request_globals_class
#提供对request_globals_class属性的的读写功能，如果写操作，则下次读取需要读取属性app_ctx_globals_class




    #: The debug flag.  Set this to `True` to enable debugging of the
    #: application.  In debug mode the debugger will kick in when an unhandled
    #: exception occurs and the integrated server will automatically reload
    #: the application if changes in the code are detected.
    #:
    #: This attribute can also be configured from the config with the `DEBUG`
    #: configuration key.  Defaults to `False`.
    debug = ConfigAttribute('DEBUG')
#设置属性debug


    #: The testing flag.  Set this to `True` to enable the test mode of
    #: Flask extensions (and in the future probably also Flask itself).
    #: For example this might activate unittest helpers that have an
    #: additional runtime cost which should not be enabled by default.
    #:
    #: If this is enabled and PROPAGATE_EXCEPTIONS is not changed from the
    #: default it's implicitly enabled.
    #:
    #: This attribute can also be configured from the config with the
    #: `TESTING` configuration key.  Defaults to `False`.
    testing = ConfigAttribute('TESTING')
#设置属性testing


    #: If a secret key is set, cryptographic components can use this to
    #: sign cookies and other things.  Set this to a complex random value
    #: when you want to use the secure cookie for instance.
    #:
    #: This attribute can also be configured from the config with the
    #: `SECRET_KEY` configuration key.  Defaults to `None`.
    secret_key = ConfigAttribute('SECRET_KEY')
#设置属性secret_key


    #: The secure cookie uses this for the name of the session cookie.
    #:
    #: This attribute can also be configured from the config with the
    #: `SESSION_COOKIE_NAME` configuration key.  Defaults to ``'session'``
    session_cookie_name = ConfigAttribute('SESSION_COOKIE_NAME')
#设置属性session_cookie_name


    #: A :class:`~datetime.timedelta` which is used to set the expiration
    #: date of a permanent session.  The default is 31 days which makes a
    #: permanent session survive for roughly one month.
    #:
    #: This attribute can also be configured from the config with the
    #: `PERMANENT_SESSION_LIFETIME` configuration key.  Defaults to
    #: ``timedelta(days=31)``
    permanent_session_lifetime = ConfigAttribute('PERMANENT_SESSION_LIFETIME',
        get_converter=_make_timedelta)
#设置属性permanent_session_lifetime 


    #: Enable this if you want to use the X-Sendfile feature.  Keep in
    #: mind that the server has to support this.  This only affects files
    #: sent with the :func:`send_file` method.
    #:
    #: .. versionadded:: 0.2
    #:
    #: This attribute can also be configured from the config with the
    #: `USE_X_SENDFILE` configuration key.  Defaults to `False`.
    use_x_sendfile = ConfigAttribute('USE_X_SENDFILE')
#设置属性use_x_sendfile


    #: The name of the logger to use.  By default the logger name is the
    #: package name passed to the constructor.
    #:
    #: .. versionadded:: 0.4
    logger_name = ConfigAttribute('LOGGER_NAME')
#设置属性logger_name


    #: Enable the deprecated module support?  This is active by default
    #: in 0.7 but will be changed to False in 0.8.  With Flask 1.0 modules
    #: will be removed in favor of Blueprints
    enable_modules = True
#设置属性enable_modules


    #: The logging format used for the debug logger.  This is only used when
    #: the application is in debug mode, otherwise the attached logging
    #: handler does the formatting.
    #:
    #: .. versionadded:: 0.3
    debug_log_format = (
        '-' * 80 + '\n' +
        '%(levelname)s in %(module)s [%(pathname)s:%(lineno)d]:\n' +
        '%(message)s\n' +
        '-' * 80
    )
#设置属性debug_log_format


    #: The JSON encoder class to use.  Defaults to :class:`~flask.json.JSONEncoder`.
    #:
    #: .. versionadded:: 0.10
    json_encoder = json.JSONEncoder
#设置属性json_encoder


    #: The JSON decoder class to use.  Defaults to :class:`~flask.json.JSONDecoder`.
    #:
    #: .. versionadded:: 0.10
    json_decoder = json.JSONDecoder
#设置属性json_decoder


    #: Options that are passed directly to the Jinja2 environment.
    jinja_options = ImmutableDict(
        extensions=['jinja2.ext.autoescape', 'jinja2.ext.with_']
    )
#设置属性jinja_options


    #: Default configuration parameters.
    default_config = ImmutableDict({
        'DEBUG':                                False,
        'TESTING':                              False,
        'PROPAGATE_EXCEPTIONS':                 None,
        'PRESERVE_CONTEXT_ON_EXCEPTION':        None,
        'SECRET_KEY':                           None,
        'PERMANENT_SESSION_LIFETIME':           timedelta(days=31),
        'USE_X_SENDFILE':                       False,
        'LOGGER_NAME':                          None,
        'SERVER_NAME':                          None,
        'APPLICATION_ROOT':                     None,
        'SESSION_COOKIE_NAME':                  'session',
        'SESSION_COOKIE_DOMAIN':                None,
        'SESSION_COOKIE_PATH':                  None,
        'SESSION_COOKIE_HTTPONLY':              True,
        'SESSION_COOKIE_SECURE':                False,
        'MAX_CONTENT_LENGTH':                   None,
        'SEND_FILE_MAX_AGE_DEFAULT':            12 * 60 * 60, # 12 hours
        'TRAP_BAD_REQUEST_ERRORS':              False,
        'TRAP_HTTP_EXCEPTIONS':                 False,
        'PREFERRED_URL_SCHEME':                 'http',
        'JSON_AS_ASCII':                        True,
        'JSON_SORT_KEYS':                       True,
        'JSONIFY_PRETTYPRINT_REGULAR':          True,
    })
#设置属性default_config，用于生成app时的初始化config配置


    #: The rule object to use for URL rules created.  This is used by
    #: :meth:`add_url_rule`.  Defaults to :class:`werkzeug.routing.Rule`.
    #:
    #: .. versionadded:: 0.7
    url_rule_class = Rule
#设置属性url_rule_class


    #: the test client that is used with when `test_client` is used.
    #:
    #: .. versionadded:: 0.7
    test_client_class = None
#设置属性test_client_class


    #: the session interface to use.  By default an instance of
    #: :class:`~flask.sessions.SecureCookieSessionInterface` is used here.
    #:
    #: .. versionadded:: 0.8
    session_interface = SecureCookieSessionInterface()
#设置属性session_interface