到目前为止，使用selenium操作headless 模式下的chrome下载文件会出现问题，点击了下载却没有任何文件被下下来。官方现在也还没有正式解决这个bug(若已解决请指正)，所以得靠自己摸索下载方法了。

在一番搜索后，终于找到了解决办法，可以在chrome headless模式下指定下载目录并且下载。出处找不到了，实现过程如下：

定义一个DriverBuilder

class DriverBuilder():
    def enable_download_in_headless_chrome(self, driver, download_dir):
        there is currently a "feature" in chrome where
        headless does not allow file download: https://bugs.chromium.org/p/chromium/issues/detail?id=696481
        This method is a hacky work-around until the official chromedriver support for this.
        Requires chrome version 62.0.3196.0 or above.
        # add missing support for chrome "send_command"  to selenium webdriver
        driver.command_executor._commands["send_command"] = ("POST", '/session/$sessionId/chromium/send_command')
        params = {'cmd': 'Page.setDownloadBehavior', 'params': {'behavior': 'allow', 'downloadPath': download_dir}}
        command_result = driver.execute("send_command", params)
        self.logger.info("response from browser:")
        for key in command_result:
            self.logger.info("result:" + key + ":" + str(command_result[key]))
配置好下载项
        self.options = webdriver.ChromeOptions()
        self.store_path = 'your_download_file'
        if not os.path.exists(self.store_path):
            os.makedirs(self.store_path)
        self.prefs = {'download.default_directory': self.store_path,'profile.default_content_settings.popups': 0}
        self.options.add_experimental_option('prefs', self.prefs)
        self.options.add_argument('--headless')
        self.driver = webdriver.Chrome(chrome_options=self.options)