download.py 文件源码

def download(self, url):

        working_dir = self.working_dir if self.working_dir else ''

        r = Resource()

        # For local files, don't download, just reference in place.
        if url.scheme == 'file':
            r.cache_path = Url(url.resource_url).path
            r.download_time = None

            # Many places the file may exist
            locations = {  # What a mess ...
                abspath(r.cache_path),
                abspath(r.cache_path.lstrip('/')),
                abspath(join(working_dir, r.cache_path)),
                abspath(r.cache_path.lstrip('/'))
            }

            for l in locations:
                if exists(l):
                    r.sys_path = l
                    break
            else:
                raise DownloadError(("File resource does not exist. Found none of:"
                                     "\n{}\n\nWorking dir = {}\ncache_path={}\nspec_path={}")
                                    .format('\n'.join(locations), working_dir, r.cache_path, url.path))

        else:
            # Not a local file, so actually need to download it.
            try:
                r.cache_path, r.download_time = self._download_with_lock(url.resource_url)
            except AccessError as e:
                # Try again, using a URL that we may have configured an account for. This is
                # primarily S3 urls, with Boto or AWS credential
                try:
                    r.cache_path, r.download_time = self._download_with_lock(url.auth_resource_url)
                except AttributeError:
                    raise e

            r.sys_path = self.cache.getsyspath(r.cache_path)

        return r