def spidercls_for_request(spider_loader, request, default_spidercls=None,
                          log_none=False, log_multiple=False):
    """Return a spider class that handles the given Request.

    This will look for the spiders that can handle the given request (using
    the spider loader) and return a Spider class if (and only if) there is
    only one Spider able to handle the Request.

    If multiple spiders (or no spider) are found, it will return the
    default_spidercls passed. It can optionally log if multiple or no spiders
    are found.
    """
    snames = spider_loader.find_by_request(request)
    if len(snames) == 1:
        return spider_loader.load(snames[0])

    if len(snames) > 1 and log_multiple:
        logger.error('More than one spider can handle: %(request)s - %(snames)s',
                     {'request': request, 'snames': ', '.join(snames)})

    if len(snames) == 0 and log_none:
        logger.error('Unable to find spider that handles: %(request)s',
                     {'request': request})

    return default_spidercls
Return a spider class that handles the given Request.

    This will look for the spiders that can handle the given request (using
    the spider loader) and return a Spider class if (and only if) there is
    only one Spider able to handle the Request.

    If multiple spiders (or no spider) are found, it will return the
    default_spidercls passed. It can optionally log if multiple or no spiders
    are found.
    
stackoverflow/venv/lib/python3.6/site-packages/scrapy/utils/spider.py