persistent cookie storage for PyQt5

from PyQt5.QtNetwork import QNetworkCookie, QNetworkCookieJar
import os


class CookieJar(QNetworkCookieJar):
    """Persistent cookie jar.

    Usage:
        self.cj = CookieJar('cookies.txt')
        self.webView.page().networkAccessManager().setCookieJar(
            self.cj)"""
    def __init__(self, filename, parent=None):
        super().__init__(parent)
        self.filename = filename
        self.load()

    def load(self):
        if os.path.isfile(self.filename):
            data = open(self.filename, 'rb').read()
            self.setAllCookies(QNetworkCookie.parseCookies(data))

    def save(self):
        f = open(self.filename, 'wb')
        for cookie in self.allCookies():
            if not cookie.isSessionCookie():
                f.write(cookie.toRawForm())
                f.write(b'\n')

    def __del__(self):
        self.save()