environment.py 文件源码

def select_template(self, names, parent=None, globals=None):
        """Works like :meth:`get_template` but tries a number of templates
        before it fails.  If it cannot find any of the templates, it will
        raise a :exc:`TemplatesNotFound` exception.

        .. versionadded:: 2.3

        .. versionchanged:: 2.4
           If `names` contains a :class:`Template` object it is returned
           from the function unchanged.
        """
        if not names:
            raise TemplatesNotFound(message=u'Tried to select from an empty list '
                                            u'of templates.')
        globals = self.make_globals(globals)
        for name in names:
            if isinstance(name, Template):
                return name
            if parent is not None:
                name = self.join_path(name, parent)
            try:
                return self._load_template(name, globals)
            except TemplateNotFound:
                pass
        raise TemplatesNotFound(names)