from PyQt5.QtWebKitWidgets import QWebView, QWebPage
from PyQt5.QtNetwork import QNetworkAccessManager
from PyQt5.QtWidgets import QApplication
from PyQt5.QtCore import QUrl, pyqtSignal
import urllib.parse

USER_AGENT = ("Mozilla/5.0 (compatible; Googlebot/2.1; "
              "+http://www.google.com/bot.html)")


class WebView(QWebView):
    def __init__(self, parent=None):
        super().__init__(parent)
        page = WebPage(self)
        nam = NetworkAccessManager(page)
        nam.loginSubmitted.connect(self.onLogin)
        page.setNetworkAccessManager(nam)
        self.setPage(page)

    def onLogin(self, username, password):
        print("Username:", username)
        print("Password:", password)


class WebPage(QWebPage):
    def userAgentForUrl(self, url):
        return USER_AGENT


class NetworkAccessManager(QNetworkAccessManager):
    loginSubmitted = pyqtSignal(str, str)

    def createRequest(self, op, req, outgoingData):
        url = req.url().toString()
        print("Request URL:", url)
        encoding = b"application/x-www-form-urlencoded"
        if (op == QNetworkAccessManager.PostOperation and
                # При авторизации через мобильную версию ссылка выглядит
                # так:
                # https://login.vk.com/?act=login&
                # _origin=https://m.vk.com&ip_h=<hash>&role=pda&utf8=1
                url.startswith("https://login.vk.com/?act=login") and
                req.rawHeader(b"content-type") == encoding):
            amount = int(req.rawHeader(b"content-length"))
            data = str(outgoingData.peek(amount), 'ascii')
            data = dict(urllib.parse.parse_qsl(data))
            self.loginSubmitted.emit(data['email'], data['pass'])
        return super().createRequest(op, req, outgoingData)


if __name__ == '__main__':
    app = QApplication([])
    web = WebView()
    web.show()
    web.load(QUrl("https://vk.com"))
    app.exec_()