• 请求钩子
  before_request after_request errorhandler

class Flask(object):
    # ...
    
    def before_request(self, f):
        """Registers a function to run before each request."""
        self.before_request_funcs.append(f)
        return f

    def after_request(self, f):
        """Register a function to be run after each request."""
        self.after_request_funcs.append(f)
        return f
    def errorhandler(self, code):
        def decorator(f):
            self.error_handlers[code] = f
            return f
        return decorator

• 装饰器
  route

class Flask(object)
    # ...
    def route(self, rule, **options):
        """
        By default a variable part
        in the URL accepts any string without a slash however a different
        converter can be specified as well by using ``<converter:name>``.   
        =========== ===========================================
        `int`       accepts integers
        `float`     like `int` but for floating point values
        `path`      like the default but also accepts slashes
        =========== ===========================================
        An important detail to keep in mind is how Flask deals with trailing
        slashes.  The idea is to keep each URL unique so the following rules
        apply:
        1. If a rule ends with a slash and is requested without a slash
           by the user, the user is automatically redirected to the same
           page with a trailing slash attached.
        2. If a rule does not end with a trailing slash and the user request
           the page with a trailing slash, a 404 not found is raised.
        The :meth:`route` decorator accepts a couple of other arguments
        as well:
        :param rule: the URL rule as string
        :param methods: a list of methods this rule should be limited
                        to (``GET``, ``POST`` etc.).  By default a rule
                        just listens for ``GET`` (and implicitly ``HEAD``).
        :param subdomain: specifies the rule for the subdoain in case
                          subdomain matching is in use.
        :param strict_slashes: can be used to disable the strict slashes
                               setting for this rule.  See above.
        :param options: other options to be forwarded to the underlying
                        :class:`~werkzeug.routing.Rule` object.
        """
        def decorator(f):
            self.add_url_rule(rule, f.__name__, **options)
            self.view_functions[f.__name__] = f
            return f
        return decorator

slash : /
例如

@app.route('/projects/')
def projects():
    pass

如果URL为：*/projects，则会重定向到/projects/。反之报404。

add_url_rule()

class Flask(object):
    # ...
    def add_url_rule(self, rule, endpoint, **options):
        """Connects a URL rule.  Works exactly like the :meth:`route`
        decorator but does not register the view function for the endpoint.
        Basically this example::
            @app.route('/')
            def index():
                pass
        Is equivalent to the following::
            def index():
                pass
            app.add_url_rule('index', '/')
            app.view_functions['index'] = index

        :param rule: the URL rule as string
        :param endpoint: the endpoint for the registered URL rule.  Flask
                         itself assumes the name of the view function as
                         endpoint
        :param options: the options to be forwarded to the underlying
                        :class:`~werkzeug.routing.Rule` object
        """
        options['endpoint'] = endpoint
        options.setdefault('methods', ('GET',))
        self.url_map.add(Rule(rule, **options))

• WSGI协议

class Flask(object):
    # ...
    def __call__(self, environ, start_response):
        """Shortcut for :attr:`wsgi_app`"""
        return self.wsgi_app(environ, start_response)