jinja2.py 文件源码

def get_jinja2(factory=Jinja2, key=_registry_key, app=None):
    """Returns an instance of :class:`Jinja2` from the app registry.

    It'll try to get it from the current app registry, and if it is not
    registered it'll be instantiated and registered. A second call to this
    function will return the same instance.

    :param factory:
        The callable used to build and register the instance if it is not yet
        registered. The default is the class :class:`Jinja2` itself.
    :param key:
        The key used to store the instance in the registry. A default is used
        if it is not set.
    :param app:
        A :class:`webapp2.WSGIApplication` instance used to store the instance.
        The active app is used if it is not set.
    """
    app = app or webapp2.get_app()
    jinja2 = app.registry.get(key)
    if not jinja2:
        jinja2 = app.registry[key] = factory(app)

    return jinja2