Reading remote file through http

remote_file.py

import io
from http import HTTPStatus
from urllib.request import Request, urlopen
from urllib.error import HTTPError


class RemoteFile(io.IOBase):
    '''
        Example of usage
        
        import zipfile
        from remote_file import RemoteFile

        zf = zipfile.ZipFile(RemoteFile('https://site.domain/remote.zip'))
        print(zf.filelist)
    '''
    def __init__(self, url):
        self._url = url
        self._offset = 0
        self.name = self._url.split('/')[-1]

        head_request = Request(url)
        head_request.get_method = lambda: 'HEAD'
        try:
            response = urlopen(head_request)
            response_info = response.info()
            self._filesize = int(response_info.get('Content-Length'))
        except HTTPError as e:
            raise IOError('could not open remote url')
        if response_info.get('Accept-Ranges') != 'bytes':
            raise IOError('remote server does not support range')

    def seek(self, offset, from_what=io.SEEK_SET):
        if from_what == io.SEEK_SET:
            self._offset = offset
        elif from_what == io.SEEK_CUR:
            self._offset += offset
        elif from_what == io.SEEK_END:
            self._offset = self._filesize + offset

    def tell(self):
        return self._offset

    def read(self, size=-1):
        if size > 0:
            start, end = self._offset, self._offset + size
        else:
            start, end = self._offset, self._filesize

        get_request = Request(self._url, headers={
            'Range': 'bytes={}-{}'.format(start, end - 1)
        })
        with urlopen(get_request) as response:
            if response.status != HTTPStatus.PARTIAL_CONTENT:
                raise IOError('could read data from remote')
            content = response.read()

        self._offset += len(content)
        return content