# Django 2.2.9.dev20191202104323 文档

# django.template.loader 源代码

    from . import engines
    from .exceptions import TemplateDoesNotExist

    def get_template(template_name, using=None):
        """
        Load and return a template for the given name.

        Raise TemplateDoesNotExist if no such template exists.
        """
        chain = []
        engines = _engine_list(using)
        for engine in engines:
            try:
                return engine.get_template(template_name)
            except TemplateDoesNotExist as e:
                chain.append(e)

        raise TemplateDoesNotExist(template_name, chain=chain)

    def select_template(template_name_list, using=None):
        """
        Load and return a template for one of the given names.

        Try names in order and return the first template found.

        Raise TemplateDoesNotExist if no such template exists.
        """
        if isinstance(template_name_list, str):
            raise TypeError(
                'select_template() takes an iterable of template names but got a '
                'string: %r. Use get_template() if you want to load a single '
                'template by name.' % template_name_list
            )

        chain = []
        engines = _engine_list(using)
        for template_name in template_name_list:
            for engine in engines:
                try:
                    return engine.get_template(template_name)
                except TemplateDoesNotExist as e:
                    chain.append(e)

        if template_name_list:
            raise TemplateDoesNotExist(', '.join(template_name_list), chain=chain)
        else:
            raise TemplateDoesNotExist("No template names provided")

    def render_to_string(template_name, context=None, request=None, using=None):
        """
        Load a template and render it with a context. Return a string.

        template_name may be a string or a list of strings.
        """
        if isinstance(template_name, (list, tuple)):
            template = select_template(template_name, using=using)
        else:
            template = get_template(template_name, using=using)
        return template.render(context, request)

    def _engine_list(using=None):
        return engines.all() if using is None else [engines[using]]