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QNetworkAccessManager https UnknownNetworkError when using pyside2

  • Hello, I’m using the QNetworkAccessManager module and it works fine with HTTP requests, but when I try to do https requests it fails and returns “PySide2.QtNetwork.QNetworkReply.NetworkError.UnknownNetworkError: TLS initialization failed”
    this problem only happens with pyside2 on windows.
    but it works fine on Mac os.
    when I used the same piece of code with pyqt5 it worked just fine on both Windows and Mac os.
    https requests:
    1.pyside2 on windows: fails
    2.pyside2 on mac: works fine
    3. pyqt5 on windows: works fine
    4. pyqt5 on mac: works fine
    and I’m stuck with it for a while and can’t seem to find the problem.

    from PySide2 import QtNetwork
    from PySide2 import QtCore
    import sys, json
    class Example:
    def __init__(self):
        self.nam = QtNetwork.QNetworkAccessManager()
    def do_request(self):
        url = ''
        req = QtNetwork.QNetworkRequest(QtCore.QUrl(url))
    def handle_response(self, reply):
        er = reply.error()
        if er == QtNetwork.QNetworkReply.NoError:
            bytes_string = reply.readAll()
            print(str(bytes_string, 'utf-8'))
            print(f'Error occurred: {er}: {reply.errorString()}')
    def main():
    app = QtCore.QCoreApplication([])
    ex = Example()
    if name == ‘main’:

    I’m using python 3.7 and pyside2 5.15

  • Lifetime Qt Champion

    Hi and welcome to devnet,

    Do you also have OpenSSL available on your machine ?

  • Yes, and when I tried to run using the command line, these errors popup.

    and I configured the environment variable to point to
    located on C:\Program Files\OpenSSL-Win64\bin
    and I'm not sure why It is searching the C:\WINDOWS path



  • Lifetime Qt Champion

    Because it's higher in the list.

    But in any case, having OpenSSL in the Windows folder is usually a bad sign. That's typically a library that shall be provided along an application and not forced there.

  • I looked into the pyside2 package installed on my machine and it seems that it doesn't come with its own libssl-1_1-x64.dll unlike pyqt5 package which comes with its own version.

    I don't know what version that pyside2 requires, and how to fix this ?!!

  • Lifetime Qt Champion

    The Qt Online Installer has an option to download a suitable version of OpenSSL.

    How are you installing PySide2 ?

  • I installed it using pip
    pip install pyside2

    I'm on windows using python 3.7