自動的に拡張子を設定して保存してくれるとラクだと思った

imageDownloader.py

import os
import time

import requests


class DownloaderError(Exception):
    pass


class Downloader:
    """
    params:
        verbose [bool]: 詳細を表示
        write_pages [bool]: download 時にファイルとして保存
        y [bool]: yes option
    """

    params = dict()

    def set_param(self, key, value):
        self.params.update({key: value})

    def get_param(self, key, default=None):
        return self.params.get(key, default)

    @property
    def NAME(self):
        return str(self.__class__.__name__).rstrip("Downloader") + "DL"

    @staticmethod
    def to_screen(msg):
        print(msg)

    def _debug_verbose(self, text):
        if self.params.get("verbose", False):
            self.to_screen(f"[{self.NAME}] {text}")

    @staticmethod
    def wait_input(msg=""):
        return input(msg).strip()

    def wait_input_yN(self, msg):
        if self.params.get("y", False):
            return True

        r = self.wait_input(f"{msg} [y/N]: ")
        if r == "y":
            return True
        return False

    def _save_as_file(self, filename, bytes_content):
        if not self.params.get("write_pages", False):
            return

        # overwrite option
        if os.path.isfile(filename):
            if not self.wait_input_yN(f"File '{filename}' already exists. Overwrite?"):
                return

        self.to_screen(f"[download] Destination: '{filename}'")
        with open(filename, "wb") as f:
            f.write(bytes_content)

    def download(self, **info_dict):
        """
        Download any data using info_dict

        Return a download content as bytes
        """
        content = self._download(**info_dict)

        assert isinstance(content, bytes)
        return content

    def _download(self, **info_dict):
        self._debug_verbose("_download() This method must be implemented by subclasses")
        return b""


class HttpDownloader(Downloader):
    def _request_webpage(self, url, params=None, **kwargs):
        """Return a Response object"""
        # https://github.com/psf/requests/blob/master/requests/api.py

        r = requests.get(url, params, **kwargs)
        self._debug_verbose(f"Response {r.status_code}: {r.url}")

        return r

    @staticmethod
    def _guess_ext_from_content_type(content_type):
        pattern = {
            "text/plain": ".txt",
            "text/html": ".html",
            "text/csv": ".csv",
            "image/jpeg": ".jpeg",
            "image/png": ".png",
            "image/gif": ".gif",
        }

        for ct, ext in pattern.items():
            if ct in content_type:
                return ext

        return ""

    def _download_webpage(self, **kwargs):
        """Return a tuple(page content as bytes, Response object)"""

        # reqiored kwargs
        url = kwargs.pop("url", None)
        if url is None:
            raise TypeError("_download() missing 1 required kwargs: 'url'")

        # optional kwargs
        params = kwargs.pop("params", None)
        filename = kwargs.pop("filename", str(time.time_ns()))

        self._debug_verbose("Downloading webpage")
        r = self._request_webpage(url, params)

        content_type = r.headers.get("Content-Type")
        ext = self._guess_ext_from_content_type(content_type)
        filename += ext

        self._save_as_file(filename, r.content)

        return (r.content, r)

    def _download(self, **kwargs):
        content, _ = self._download_webpage(**kwargs)
        return content


class ImageDownloader(HttpDownloader):
    @staticmethod
    def _guess_ext_from_content_type(content_type):
        pattern = {
           "image/jpeg": ".jpeg",
           "image/png": ".png",
           "image/gif": ".gif",
        }

        for ct, ext in pattern.items():
            if ct in content_type:
                return ext

        raise DownloaderError(f"Undefined or Non image content-type: {content_type}")

    def _download(self, **kwargs):
        self.params.update({"write_pages": True})
        content, _ = self._download_webpage(**kwargs)
        return content


if __name__ == "__main__":
    idl = ImageDownloader()
    idl.set_param("verbose", True)
    idl.download(url="https://example.com", filename="test")